Annual report pursuant to Section 13 and 15(d)

Schedule III - Real Estate and Accumulated Depreciation (Detail)

v2.4.1.9
Schedule III - Real Estate and Accumulated Depreciation (Detail) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost $ 458,592us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances      
Land, Initial Cost 88,378us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand      
Buildings & Improvements, Initial Cost 602,477us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements      
Improvement Costs Capitalized Subsequent to Acquisition 31,710good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements      
Land, Total cost 88,394us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand      
Buildings & Improvements, Total cost 634,171us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements      
Total 722,565us-gaap_RealEstateGrossAtCarryingValue 642,353us-gaap_RealEstateGrossAtCarryingValue 533,753us-gaap_RealEstateGrossAtCarryingValue 442,521us-gaap_RealEstateGrossAtCarryingValue
Accumulated Depreciation 92,133us-gaap_RealEstateAccumulatedDepreciation 81,241us-gaap_RealEstateAccumulatedDepreciation 65,730us-gaap_RealEstateAccumulatedDepreciation 53,784us-gaap_RealEstateAccumulatedDepreciation
Net Real Estate 630,432us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet      
Raleigh, North Carolina Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 4,796us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RaleighNorthCarolinaOfficeBuildingMember
     
Land, Initial Cost 960us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RaleighNorthCarolinaOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 4,481us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RaleighNorthCarolinaOfficeBuildingMember
     
Land, Total cost 960us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RaleighNorthCarolinaOfficeBuildingMember
     
Buildings & Improvements, Total cost 4,481us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RaleighNorthCarolinaOfficeBuildingMember
     
Total 5,441us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RaleighNorthCarolinaOfficeBuildingMember
     
Accumulated Depreciation 1,773us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RaleighNorthCarolinaOfficeBuildingMember
     
Net Real Estate 3,668us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RaleighNorthCarolinaOfficeBuildingMember
     
Year Construction/ Improvements 1997      
Date Acquired Dec. 23, 2003      
Canton, Ohio Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 2,664us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CantonOhioOfficeAndWarehouseBuildingMember
     
Land, Initial Cost 186us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CantonOhioOfficeAndWarehouseBuildingMember
     
Buildings & Improvements, Initial Cost 3,083us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CantonOhioOfficeAndWarehouseBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 500good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CantonOhioOfficeAndWarehouseBuildingMember
     
Land, Total cost 186us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CantonOhioOfficeAndWarehouseBuildingMember
     
Buildings & Improvements, Total cost 3,583us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CantonOhioOfficeAndWarehouseBuildingMember
     
Total 3,769us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CantonOhioOfficeAndWarehouseBuildingMember
     
Accumulated Depreciation 972us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CantonOhioOfficeAndWarehouseBuildingMember
     
Net Real Estate 2,797us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CantonOhioOfficeAndWarehouseBuildingMember
     
Year Construction/ Improvements 1994      
Date Acquired Jan. 30, 2004      
Akron, Ohio Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 6,828us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AkronOhioOfficeAndLaboratoryBuildingMember
     
Land, Initial Cost 1,973us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AkronOhioOfficeAndLaboratoryBuildingMember
     
Buildings & Improvements, Initial Cost 6,771us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AkronOhioOfficeAndLaboratoryBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 1,279good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AkronOhioOfficeAndLaboratoryBuildingMember
     
Land, Total cost 1,973us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AkronOhioOfficeAndLaboratoryBuildingMember
     
Buildings & Improvements, Total cost 8,050us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AkronOhioOfficeAndLaboratoryBuildingMember
     
Total 10,023us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AkronOhioOfficeAndLaboratoryBuildingMember
     
Accumulated Depreciation 1,916us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AkronOhioOfficeAndLaboratoryBuildingMember
     
Net Real Estate 8,107us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AkronOhioOfficeAndLaboratoryBuildingMember
     
Year Construction/ Improvements 1968      
Year Construction/Improvements One 1999      
Date Acquired Apr. 29, 2004      
Charlotte, North Carolina Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 6,308us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CharlotteNorthCarolinaOfficeBuildingMember
     
Land, Initial Cost 740us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CharlotteNorthCarolinaOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 8,423us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CharlotteNorthCarolinaOfficeBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 61good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CharlotteNorthCarolinaOfficeBuildingMember
     
Land, Total cost 740us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CharlotteNorthCarolinaOfficeBuildingMember
     
Buildings & Improvements, Total cost 8,484us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CharlotteNorthCarolinaOfficeBuildingMember
     
Total 9,224us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CharlotteNorthCarolinaOfficeBuildingMember
     
Accumulated Depreciation 2,319us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CharlotteNorthCarolinaOfficeBuildingMember
     
Net Real Estate 6,905us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CharlotteNorthCarolinaOfficeBuildingMember
     
Year Construction/ Improvements 1984      
Year Construction/Improvements One 1995      
Date Acquired Jun. 30, 2004      
Canton, North Carolina Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 3,652us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CantonNorthCarolinaCommercialAndManufacturingBuildingMember
     
Land, Initial Cost 150us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CantonNorthCarolinaCommercialAndManufacturingBuildingMember
     
Buildings & Improvements, Initial Cost 5,050us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CantonNorthCarolinaCommercialAndManufacturingBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 7,285good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CantonNorthCarolinaCommercialAndManufacturingBuildingMember
     
Land, Total cost 150us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CantonNorthCarolinaCommercialAndManufacturingBuildingMember
     
Buildings & Improvements, Total cost 12,335us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CantonNorthCarolinaCommercialAndManufacturingBuildingMember
     
Total 12,485us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CantonNorthCarolinaCommercialAndManufacturingBuildingMember
     
Accumulated Depreciation 1,401us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CantonNorthCarolinaCommercialAndManufacturingBuildingMember
     
Net Real Estate 11,084us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CantonNorthCarolinaCommercialAndManufacturingBuildingMember
     
Year Construction/ Improvements 1998      
Year Construction/Improvements One 2014      
Date Acquired Jul. 06, 2004      
Crenshaw, Pennsylvania Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 5,176us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SnyderTownshipPennsylvaniaCommercialAndWarehouseBuildingMember
     
Land, Initial Cost 100us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SnyderTownshipPennsylvaniaCommercialAndWarehouseBuildingMember
     
Buildings & Improvements, Initial Cost 6,574us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SnyderTownshipPennsylvaniaCommercialAndWarehouseBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 269good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SnyderTownshipPennsylvaniaCommercialAndWarehouseBuildingMember
     
Land, Total cost 100us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SnyderTownshipPennsylvaniaCommercialAndWarehouseBuildingMember
     
Buildings & Improvements, Total cost 6,843us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SnyderTownshipPennsylvaniaCommercialAndWarehouseBuildingMember
     
Total 6,943us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SnyderTownshipPennsylvaniaCommercialAndWarehouseBuildingMember
     
Accumulated Depreciation 1,800us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SnyderTownshipPennsylvaniaCommercialAndWarehouseBuildingMember
     
Net Real Estate 5,143us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SnyderTownshipPennsylvaniaCommercialAndWarehouseBuildingMember
     
Year Construction/ Improvements 1991      
Date Acquired Aug. 05, 2004      
Lexington, North Carolina Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 2,636us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_LexingtonNorthCarolinaCommercialAndWarehouseBuildingMember
     
Land, Initial Cost 820us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_LexingtonNorthCarolinaCommercialAndWarehouseBuildingMember
     
Buildings & Improvements, Initial Cost 2,107us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_LexingtonNorthCarolinaCommercialAndWarehouseBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 69good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_LexingtonNorthCarolinaCommercialAndWarehouseBuildingMember
     
Land, Total cost 820us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_LexingtonNorthCarolinaCommercialAndWarehouseBuildingMember
     
Buildings & Improvements, Total cost 2,176us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_LexingtonNorthCarolinaCommercialAndWarehouseBuildingMember
     
Total 2,996us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_LexingtonNorthCarolinaCommercialAndWarehouseBuildingMember
     
Accumulated Depreciation 584us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_LexingtonNorthCarolinaCommercialAndWarehouseBuildingMember
     
Net Real Estate 2,412us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_LexingtonNorthCarolinaCommercialAndWarehouseBuildingMember
     
Year Construction/ Improvements 1986      
Date Acquired Aug. 05, 2004      
Austin, Texas Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 6,500us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AustinTexasOfficeBuildingMember
     
Land, Initial Cost 1,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AustinTexasOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 6,296us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AustinTexasOfficeBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 1,396good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AustinTexasOfficeBuildingMember
     
Land, Total cost 1,000us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AustinTexasOfficeBuildingMember
     
Buildings & Improvements, Total cost 7,692us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AustinTexasOfficeBuildingMember
     
Total 8,692us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AustinTexasOfficeBuildingMember
     
Accumulated Depreciation 1,726us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AustinTexasOfficeBuildingMember
     
Net Real Estate 6,966us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AustinTexasOfficeBuildingMember
     
Year Construction/ Improvements 2001      
Date Acquired Sep. 16, 2004      
Mt. Pocono, Pennsylvania Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 4,889us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MtPoconoPennsylvaniaCommercialAndManufacturingBuildingMember
     
Land, Initial Cost 350us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MtPoconoPennsylvaniaCommercialAndManufacturingBuildingMember
     
Buildings & Improvements, Initial Cost 5,819us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MtPoconoPennsylvaniaCommercialAndManufacturingBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 18good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MtPoconoPennsylvaniaCommercialAndManufacturingBuildingMember
     
Land, Total cost 350us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MtPoconoPennsylvaniaCommercialAndManufacturingBuildingMember
     
Buildings & Improvements, Total cost 5,837us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MtPoconoPennsylvaniaCommercialAndManufacturingBuildingMember
     
Total 6,187us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MtPoconoPennsylvaniaCommercialAndManufacturingBuildingMember
     
Accumulated Depreciation 1,551us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MtPoconoPennsylvaniaCommercialAndManufacturingBuildingMember
     
Net Real Estate 4,636us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MtPoconoPennsylvaniaCommercialAndManufacturingBuildingMember
     
Year Construction/ Improvements 1995      
Year Construction/Improvements One 1999      
Date Acquired Oct. 15, 2004      
San Antonio, Texas Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 6,643us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SanAntonioTexasFlexibleOfficeBuildingMember
     
Land, Initial Cost 843us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SanAntonioTexasFlexibleOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 7,514us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SanAntonioTexasFlexibleOfficeBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 621good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SanAntonioTexasFlexibleOfficeBuildingMember
     
Land, Total cost 843us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SanAntonioTexasFlexibleOfficeBuildingMember
     
Buildings & Improvements, Total cost 8,135us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SanAntonioTexasFlexibleOfficeBuildingMember
     
Total 8,978us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SanAntonioTexasFlexibleOfficeBuildingMember
     
Accumulated Depreciation 2,389us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SanAntonioTexasFlexibleOfficeBuildingMember
     
Net Real Estate 6,589us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SanAntonioTexasFlexibleOfficeBuildingMember
     
Year Construction/ Improvements 1999      
Date Acquired Feb. 10, 2005      
Columbus, Ohio Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 2,516us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioIndustrialBuildingMember
     
Land, Initial Cost 410us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 2,385us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioIndustrialBuildingMember
     
Land, Total cost 410us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioIndustrialBuildingMember
     
Buildings & Improvements, Total cost 2,385us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioIndustrialBuildingMember
     
Total 2,795us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioIndustrialBuildingMember
     
Accumulated Depreciation 610us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioIndustrialBuildingMember
     
Net Real Estate 2,185us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioIndustrialBuildingMember
     
Year Construction/ Improvements 1995      
Date Acquired Feb. 10, 2005      
Big Flats, New York Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 5,365us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BigFlatsNewYorkIndustrialBuildingMember
     
Land, Initial Cost 275us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BigFlatsNewYorkIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 6,459us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BigFlatsNewYorkIndustrialBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 34good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BigFlatsNewYorkIndustrialBuildingMember
     
Land, Total cost 275us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BigFlatsNewYorkIndustrialBuildingMember
     
Buildings & Improvements, Total cost 6,493us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BigFlatsNewYorkIndustrialBuildingMember
     
Total 6,768us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BigFlatsNewYorkIndustrialBuildingMember
     
Accumulated Depreciation 1,623us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BigFlatsNewYorkIndustrialBuildingMember
     
Net Real Estate 5,145us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BigFlatsNewYorkIndustrialBuildingMember
     
Year Construction/ Improvements 2001      
Date Acquired Apr. 15, 2005      
Wichita, Kansas Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 7,466us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_WichitaKansasOfficeBuildingMember
     
Land, Initial Cost 1,525us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_WichitaKansasOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 9,703us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_WichitaKansasOfficeBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 77good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_WichitaKansasOfficeBuildingMember
     
Land, Total cost 1,525us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_WichitaKansasOfficeBuildingMember
     
Buildings & Improvements, Total cost 9,780us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_WichitaKansasOfficeBuildingMember
     
Total 11,305us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_WichitaKansasOfficeBuildingMember
     
Accumulated Depreciation 2,510us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_WichitaKansasOfficeBuildingMember
     
Net Real Estate 8,795us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_WichitaKansasOfficeBuildingMember
     
Year Construction/ Improvements 2000      
Date Acquired May 18, 2005      
Arlington, Texas Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 3,814us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ArlingtonTexasWarehouseAndBakeryBuildingMember
     
Land, Initial Cost 636us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ArlingtonTexasWarehouseAndBakeryBuildingMember
     
Buildings & Improvements, Initial Cost 3,695us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ArlingtonTexasWarehouseAndBakeryBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 416good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ArlingtonTexasWarehouseAndBakeryBuildingMember
     
Land, Total cost 636us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ArlingtonTexasWarehouseAndBakeryBuildingMember
     
Buildings & Improvements, Total cost 4,111us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ArlingtonTexasWarehouseAndBakeryBuildingMember
     
Total 4,747us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ArlingtonTexasWarehouseAndBakeryBuildingMember
     
Accumulated Depreciation 1,012us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ArlingtonTexasWarehouseAndBakeryBuildingMember
     
Net Real Estate 3,735us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ArlingtonTexasWarehouseAndBakeryBuildingMember
     
Year Construction/ Improvements 1966      
Date Acquired May 26, 2005      
Dayton, Ohio Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 1,877us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DaytonOhioOfficeBuildingMember
     
Land, Initial Cost 525us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DaytonOhioOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 1,877us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DaytonOhioOfficeBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 120good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DaytonOhioOfficeBuildingMember
     
Land, Total cost 525us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DaytonOhioOfficeBuildingMember
     
Buildings & Improvements, Total cost 1,997us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DaytonOhioOfficeBuildingMember
     
Total 2,522us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DaytonOhioOfficeBuildingMember
     
Accumulated Depreciation 820us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DaytonOhioOfficeBuildingMember
     
Net Real Estate 1,702us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DaytonOhioOfficeBuildingMember
     
Year Construction/ Improvements 1956      
Date Acquired Jun. 30, 2005      
Eatontown, New Jersey Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 4,365us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EatontownNewJerseyOfficeBuildingMember
     
Land, Initial Cost 1,351us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EatontownNewJerseyOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 3,520us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EatontownNewJerseyOfficeBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 534good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EatontownNewJerseyOfficeBuildingMember
     
Land, Total cost 1,351us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EatontownNewJerseyOfficeBuildingMember
     
Buildings & Improvements, Total cost 4,054us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EatontownNewJerseyOfficeBuildingMember
     
Total 5,405us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EatontownNewJerseyOfficeBuildingMember
     
Accumulated Depreciation 1,012us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EatontownNewJerseyOfficeBuildingMember
     
Net Real Estate 4,393us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EatontownNewJerseyOfficeBuildingMember
     
Year Construction/ Improvements 1991      
Date Acquired Jul. 07, 2005      
Frankling Township, New Jersey Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 6,471us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FranklingTownshipNewJerseyOfficeAndWarehouseBuildingMember
     
Land, Initial Cost 1,632us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FranklingTownshipNewJerseyOfficeAndWarehouseBuildingMember
     
Buildings & Improvements, Initial Cost 6,200us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FranklingTownshipNewJerseyOfficeAndWarehouseBuildingMember
     
Land, Total cost 1,632us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FranklingTownshipNewJerseyOfficeAndWarehouseBuildingMember
     
Buildings & Improvements, Total cost 6,200us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FranklingTownshipNewJerseyOfficeAndWarehouseBuildingMember
     
Total 7,832us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FranklingTownshipNewJerseyOfficeAndWarehouseBuildingMember
     
Accumulated Depreciation 1,514us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FranklingTownshipNewJerseyOfficeAndWarehouseBuildingMember
     
Net Real Estate 6,318us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FranklingTownshipNewJerseyOfficeAndWarehouseBuildingMember
     
Year Construction/ Improvements 1978      
Date Acquired Jul. 11, 2005      
Duncan, South Carolina Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 10,375us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DuncanSouthCarolinaOfficeAndWarehouseBuildingMember
     
Land, Initial Cost 783us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DuncanSouthCarolinaOfficeAndWarehouseBuildingMember
     
Buildings & Improvements, Initial Cost 10,790us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DuncanSouthCarolinaOfficeAndWarehouseBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 1,615good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DuncanSouthCarolinaOfficeAndWarehouseBuildingMember
     
Land, Total cost 783us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DuncanSouthCarolinaOfficeAndWarehouseBuildingMember
     
Buildings & Improvements, Total cost 12,405us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DuncanSouthCarolinaOfficeAndWarehouseBuildingMember
     
Total 13,188us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DuncanSouthCarolinaOfficeAndWarehouseBuildingMember
     
Accumulated Depreciation 2,979us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DuncanSouthCarolinaOfficeAndWarehouseBuildingMember
     
Net Real Estate 10,209us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DuncanSouthCarolinaOfficeAndWarehouseBuildingMember
     
Year Construction/ Improvements 1984      
Year Construction/Improvements One 2001      
Year Construction/Improvements Two 2007      
Date Acquired Jul. 14, 2005      
Duncan, South Carolina Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 2,579us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DuncanSouthCarolinaManufacturingBuildingMember
     
Land, Initial Cost 195us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DuncanSouthCarolinaManufacturingBuildingMember
     
Buildings & Improvements, Initial Cost 2,682us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DuncanSouthCarolinaManufacturingBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 419good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DuncanSouthCarolinaManufacturingBuildingMember
     
Land, Total cost 195us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DuncanSouthCarolinaManufacturingBuildingMember
     
Buildings & Improvements, Total cost 3,101us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DuncanSouthCarolinaManufacturingBuildingMember
     
Total 3,296us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DuncanSouthCarolinaManufacturingBuildingMember
     
Accumulated Depreciation 740us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DuncanSouthCarolinaManufacturingBuildingMember
     
Net Real Estate 2,556us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DuncanSouthCarolinaManufacturingBuildingMember
     
Year Construction/ Improvements 1984      
Year Construction/Improvements One 2001      
Year Construction/Improvements Two 2007      
Date Acquired Jul. 14, 2005      
Hazelwood, Missouri Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 2,291us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HazelwoodMissouriOfficeAndWarehouseBuildingMember
     
Land, Initial Cost 763us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HazelwoodMissouriOfficeAndWarehouseBuildingMember
     
Buildings & Improvements, Initial Cost 2,309us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HazelwoodMissouriOfficeAndWarehouseBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 683good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HazelwoodMissouriOfficeAndWarehouseBuildingMember
     
Land, Total cost 763us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HazelwoodMissouriOfficeAndWarehouseBuildingMember
     
Buildings & Improvements, Total cost 2,992us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HazelwoodMissouriOfficeAndWarehouseBuildingMember
     
Total 3,755us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HazelwoodMissouriOfficeAndWarehouseBuildingMember
     
Accumulated Depreciation 642us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HazelwoodMissouriOfficeAndWarehouseBuildingMember
     
Net Real Estate 3,113us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HazelwoodMissouriOfficeAndWarehouseBuildingMember
     
Year Construction/ Improvements 1977      
Date Acquired Aug. 05, 2005      
Angola, Indiana Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 626us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AngolaIndianaIndustrialBuildingMember
     
Land, Initial Cost 66us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AngolaIndianaIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 1,075us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AngolaIndianaIndustrialBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 49good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AngolaIndianaIndustrialBuildingMember
     
Land, Total cost 66us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AngolaIndianaIndustrialBuildingMember
     
Buildings & Improvements, Total cost 1,124us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AngolaIndianaIndustrialBuildingMember
     
Total 1,190us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AngolaIndianaIndustrialBuildingMember
     
Accumulated Depreciation 271us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AngolaIndianaIndustrialBuildingMember
     
Net Real Estate 919us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AngolaIndianaIndustrialBuildingMember
     
Year Construction/ Improvements 1982      
Date Acquired Sep. 02, 2005      
Angola, Indiana Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 601us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AngolaIndianaIndustrialBuildingOneMember
     
Land, Initial Cost 132us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AngolaIndianaIndustrialBuildingOneMember
     
Buildings & Improvements, Initial Cost 1,130us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AngolaIndianaIndustrialBuildingOneMember
     
Improvement Costs Capitalized Subsequent to Acquisition 51good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AngolaIndianaIndustrialBuildingOneMember
     
Land, Total cost 132us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AngolaIndianaIndustrialBuildingOneMember
     
Buildings & Improvements, Total cost 1,181us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AngolaIndianaIndustrialBuildingOneMember
     
Total 1,313us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AngolaIndianaIndustrialBuildingOneMember
     
Accumulated Depreciation 421us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AngolaIndianaIndustrialBuildingOneMember
     
Net Real Estate 892us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AngolaIndianaIndustrialBuildingOneMember
     
Year Construction/ Improvements 1998      
Date Acquired Sep. 02, 2005      
Rock Falls, Illinois Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 626us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RockFallsIllinoisIndustrialBuildingMember
     
Land, Initial Cost 35us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RockFallsIllinoisIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 1,113us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RockFallsIllinoisIndustrialBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 50good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RockFallsIllinoisIndustrialBuildingMember
     
Land, Total cost 35us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RockFallsIllinoisIndustrialBuildingMember
     
Buildings & Improvements, Total cost 1,163us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RockFallsIllinoisIndustrialBuildingMember
     
Total 1,198us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RockFallsIllinoisIndustrialBuildingMember
     
Accumulated Depreciation 144us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RockFallsIllinoisIndustrialBuildingMember
     
Net Real Estate 1,054us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RockFallsIllinoisIndustrialBuildingMember
     
Year Construction/ Improvements 1988      
Date Acquired Sep. 02, 2005      
Newburyport, Massachusetts Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 6,276us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NewburyportMassachusettsIndustrialBuildingMember
     
Land, Initial Cost 629us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NewburyportMassachusettsIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 6,504us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NewburyportMassachusettsIndustrialBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 1,847good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NewburyportMassachusettsIndustrialBuildingMember
     
Land, Total cost 629us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NewburyportMassachusettsIndustrialBuildingMember
     
Buildings & Improvements, Total cost 8,351us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NewburyportMassachusettsIndustrialBuildingMember
     
Total 8,980us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NewburyportMassachusettsIndustrialBuildingMember
     
Accumulated Depreciation 1,873us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NewburyportMassachusettsIndustrialBuildingMember
     
Net Real Estate 7,107us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NewburyportMassachusettsIndustrialBuildingMember
     
Year Construction/ Improvements 1994      
Date Acquired Oct. 17, 2005      
Clintonville, Wisconsin Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 2,997us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ClintonvilleWisconsinIndustrialManufacturingBuildingMember
     
Land, Initial Cost 55us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ClintonvilleWisconsinIndustrialManufacturingBuildingMember
     
Buildings & Improvements, Initial Cost 4,717us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ClintonvilleWisconsinIndustrialManufacturingBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 3,250good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ClintonvilleWisconsinIndustrialManufacturingBuildingMember
     
Land, Total cost 55us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ClintonvilleWisconsinIndustrialManufacturingBuildingMember
     
Buildings & Improvements, Total cost 7,967us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ClintonvilleWisconsinIndustrialManufacturingBuildingMember
     
Total 8,022us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ClintonvilleWisconsinIndustrialManufacturingBuildingMember
     
Accumulated Depreciation 1,316us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ClintonvilleWisconsinIndustrialManufacturingBuildingMember
     
Net Real Estate 6,706us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ClintonvilleWisconsinIndustrialManufacturingBuildingMember
     
Year Construction/ Improvements 1992      
Year Construction/Improvements One 2013      
Date Acquired Oct. 31, 2005      
Maple Heights, Ohio Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 9,790us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MapleHeightsOhioIndustrialBuildingMember
     
Land, Initial Cost 1,609us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MapleHeightsOhioIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 10,065us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MapleHeightsOhioIndustrialBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 1,221good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MapleHeightsOhioIndustrialBuildingMember
     
Land, Total cost 1,609us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MapleHeightsOhioIndustrialBuildingMember
     
Buildings & Improvements, Total cost 11,286us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MapleHeightsOhioIndustrialBuildingMember
     
Total 12,895us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MapleHeightsOhioIndustrialBuildingMember
     
Accumulated Depreciation 3,237us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MapleHeightsOhioIndustrialBuildingMember
     
Net Real Estate 9,658us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MapleHeightsOhioIndustrialBuildingMember
     
Year Construction/ Improvements 1974      
Date Acquired Dec. 21, 2005      
Richmond, Virginia Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 5,275us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RichmondVirginiaIndustrialBuildingMember
     
Land, Initial Cost 736us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RichmondVirginiaIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 5,336us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RichmondVirginiaIndustrialBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 36good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RichmondVirginiaIndustrialBuildingMember
     
Land, Total cost 736us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RichmondVirginiaIndustrialBuildingMember
     
Buildings & Improvements, Total cost 5,372us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RichmondVirginiaIndustrialBuildingMember
     
Total 6,108us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RichmondVirginiaIndustrialBuildingMember
     
Accumulated Depreciation 1,286us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RichmondVirginiaIndustrialBuildingMember
     
Net Real Estate 4,822us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RichmondVirginiaIndustrialBuildingMember
     
Year Construction/ Improvements 1972      
Date Acquired Dec. 30, 2005      
Toledo, Ohio Medical Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 2,750us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ToledoOhioIndustrialBuildingMember
     
Land, Initial Cost 263us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ToledoOhioIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 2,812us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ToledoOhioIndustrialBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 390good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ToledoOhioIndustrialBuildingMember
     
Land, Total cost 263us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ToledoOhioIndustrialBuildingMember
     
Buildings & Improvements, Total cost 3,202us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ToledoOhioIndustrialBuildingMember
     
Total 3,465us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ToledoOhioIndustrialBuildingMember
     
Accumulated Depreciation 736us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ToledoOhioIndustrialBuildingMember
     
Net Real Estate 2,729us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ToledoOhioIndustrialBuildingMember
     
Year Construction/ Improvements 1979      
Date Acquired Dec. 30, 2005      
South Hadley, Massachusetts Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 471us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SouthHadleyMassachusettsIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 2,765us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SouthHadleyMassachusettsIndustrialBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 71good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SouthHadleyMassachusettsIndustrialBuildingMember
     
Land, Total cost 471us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SouthHadleyMassachusettsIndustrialBuildingMember
     
Buildings & Improvements, Total cost 2,836us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SouthHadleyMassachusettsIndustrialBuildingMember
     
Total 3,307us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SouthHadleyMassachusettsIndustrialBuildingMember
     
Accumulated Depreciation 637us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SouthHadleyMassachusettsIndustrialBuildingMember
     
Net Real Estate 2,670us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SouthHadleyMassachusettsIndustrialBuildingMember
     
Year Construction/ Improvements 1978      
Date Acquired Feb. 15, 2006      
Champaign, Illinois Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 1,545us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingOneMember
     
Land, Initial Cost 687us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingOneMember
     
Buildings & Improvements, Initial Cost 2,036us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingOneMember
     
Improvement Costs Capitalized Subsequent to Acquisition 2good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingOneMember
     
Land, Total cost 687us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingOneMember
     
Buildings & Improvements, Total cost 2,038us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingOneMember
     
Total 2,725us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingOneMember
     
Accumulated Depreciation 495us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingOneMember
     
Net Real Estate 2,230us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingOneMember
     
Year Construction/ Improvements 1996      
Date Acquired Feb. 21, 2006      
Champaign, Illinois Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 3,030us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingTwoMember
     
Land, Initial Cost 1,347us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingTwoMember
     
Buildings & Improvements, Initial Cost 3,992us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingTwoMember
     
Improvement Costs Capitalized Subsequent to Acquisition 4good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingTwoMember
     
Land, Total cost 1,347us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingTwoMember
     
Buildings & Improvements, Total cost 3,996us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingTwoMember
     
Total 5,343us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingTwoMember
     
Accumulated Depreciation 971us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingTwoMember
     
Net Real Estate 4,372us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingTwoMember
     
Year Construction/ Improvements 1996      
Date Acquired Feb. 21, 2006      
Champaign, Illinois Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 1,894us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingThreeMember
     
Land, Initial Cost 842us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingThreeMember
     
Buildings & Improvements, Initial Cost 2,495us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingThreeMember
     
Improvement Costs Capitalized Subsequent to Acquisition 2good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingThreeMember
     
Land, Total cost 842us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingThreeMember
     
Buildings & Improvements, Total cost 2,497us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingThreeMember
     
Total 3,339us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingThreeMember
     
Accumulated Depreciation 607us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingThreeMember
     
Net Real Estate 2,732us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingThreeMember
     
Year Construction/ Improvements 1996      
Date Acquired Feb. 21, 2006      
Champaign, Illinois Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 1,731us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingFourMember
     
Land, Initial Cost 770us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingFourMember
     
Buildings & Improvements, Initial Cost 2,281us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingFourMember
     
Improvement Costs Capitalized Subsequent to Acquisition 2good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingFourMember
     
Land, Total cost 770us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingFourMember
     
Buildings & Improvements, Total cost 2,283us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingFourMember
     
Total 3,053us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingFourMember
     
Accumulated Depreciation 555us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingFourMember
     
Net Real Estate 2,498us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChampaignIllinoisOfficeBuildingFourMember
     
Year Construction/ Improvements 1996      
Date Acquired Feb. 21, 2006      
Burnsville, Minnesota Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 11,001us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BurnsvilleMinnesotaOfficeBuildingMember
     
Land, Initial Cost 3,511us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BurnsvilleMinnesotaOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 8,746us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BurnsvilleMinnesotaOfficeBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 3,525good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BurnsvilleMinnesotaOfficeBuildingMember
     
Land, Total cost 3,511us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BurnsvilleMinnesotaOfficeBuildingMember
     
Buildings & Improvements, Total cost 12,271us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BurnsvilleMinnesotaOfficeBuildingMember
     
Total 15,782us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BurnsvilleMinnesotaOfficeBuildingMember
     
Accumulated Depreciation 2,515us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BurnsvilleMinnesotaOfficeBuildingMember
     
Net Real Estate 13,267us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BurnsvilleMinnesotaOfficeBuildingMember
     
Year Construction/ Improvements 1984      
Date Acquired May 10, 2006      
Menomonee Falls, Wisconsin Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 6,738us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MenomoneeFallsWisconsinIndustrialBuildingMember
     
Land, Initial Cost 625us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MenomoneeFallsWisconsinIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 6,911us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MenomoneeFallsWisconsinIndustrialBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 57good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MenomoneeFallsWisconsinIndustrialBuildingMember
     
Land, Total cost 625us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MenomoneeFallsWisconsinIndustrialBuildingMember
     
Buildings & Improvements, Total cost 6,968us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MenomoneeFallsWisconsinIndustrialBuildingMember
     
Total 7,593us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MenomoneeFallsWisconsinIndustrialBuildingMember
     
Accumulated Depreciation 1,553us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MenomoneeFallsWisconsinIndustrialBuildingMember
     
Net Real Estate 6,040us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MenomoneeFallsWisconsinIndustrialBuildingMember
     
Year Construction/ Improvements 1986      
Year Construction/Improvements One 2000      
Date Acquired Jun. 30, 2006      
Baytown, Texas Medical Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 2,000us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BaytownTexasOfficeBuildingMember
     
Land, Initial Cost 221us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BaytownTexasOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 2,443us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BaytownTexasOfficeBuildingMember
     
Land, Total cost 221us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BaytownTexasOfficeBuildingMember
     
Buildings & Improvements, Total cost 2,443us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BaytownTexasOfficeBuildingMember
     
Total 2,664us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BaytownTexasOfficeBuildingMember
     
Accumulated Depreciation 593us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BaytownTexasOfficeBuildingMember
     
Net Real Estate 2,071us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BaytownTexasOfficeBuildingMember
     
Year Construction/ Improvements 1997      
Date Acquired Jul. 11, 2006      
Birmingham, Alabama Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 612us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BirminghamAlabamaIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 2,326us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BirminghamAlabamaIndustrialBuildingMember
     
Land, Total cost 612us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BirminghamAlabamaIndustrialBuildingMember
     
Buildings & Improvements, Total cost 2,326us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BirminghamAlabamaIndustrialBuildingMember
     
Total 2,938us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BirminghamAlabamaIndustrialBuildingMember
     
Accumulated Depreciation 504us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BirminghamAlabamaIndustrialBuildingMember
     
Net Real Estate 2,434us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BirminghamAlabamaIndustrialBuildingMember
     
Year Construction/ Improvements 1961      
Year Construction/Improvements One 1980      
Date Acquired Sep. 29, 2006      
Montgomery, Alabama Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 222us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MontgomeryAlabamaIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 844us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MontgomeryAlabamaIndustrialBuildingMember
     
Land, Total cost 222us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MontgomeryAlabamaIndustrialBuildingMember
     
Buildings & Improvements, Total cost 844us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MontgomeryAlabamaIndustrialBuildingMember
     
Total 1,066us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MontgomeryAlabamaIndustrialBuildingMember
     
Accumulated Depreciation 183us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MontgomeryAlabamaIndustrialBuildingMember
     
Net Real Estate 883us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MontgomeryAlabamaIndustrialBuildingMember
     
Year Construction/ Improvements 1962      
Year Construction/Improvements One 1989      
Date Acquired Sep. 29, 2006      
Columbia, Missouri Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 146us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbiaMissouriIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 555us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbiaMissouriIndustrialBuildingMember
     
Land, Total cost 146us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbiaMissouriIndustrialBuildingMember
     
Buildings & Improvements, Total cost 555us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbiaMissouriIndustrialBuildingMember
     
Total 701us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbiaMissouriIndustrialBuildingMember
     
Accumulated Depreciation 120us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbiaMissouriIndustrialBuildingMember
     
Net Real Estate 581us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbiaMissouriIndustrialBuildingMember
     
Year Construction/ Improvements 1978      
Date Acquired Sep. 29, 2006      
Mason, Ohio Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 4,250us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MasonOhioOfficeBuildingMember
     
Land, Initial Cost 797us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MasonOhioOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 6,258us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MasonOhioOfficeBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 540good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MasonOhioOfficeBuildingMember
     
Land, Total cost 797us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MasonOhioOfficeBuildingMember
     
Buildings & Improvements, Total cost 6,798us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MasonOhioOfficeBuildingMember
     
Total 7,595us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MasonOhioOfficeBuildingMember
     
Accumulated Depreciation 1,563us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MasonOhioOfficeBuildingMember
     
Net Real Estate 6,032us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MasonOhioOfficeBuildingMember
     
Year Construction/ Improvements 2002      
Date Acquired Jan. 05, 2007      
Raleigh, North Carolina Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 5,164us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RaleighNorthCarolinaIndustrialBuildingMember
     
Land, Initial Cost 1,606us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RaleighNorthCarolinaIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 5,513us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RaleighNorthCarolinaIndustrialBuildingMember
     
Land, Total cost 1,606us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RaleighNorthCarolinaIndustrialBuildingMember
     
Buildings & Improvements, Total cost 5,513us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RaleighNorthCarolinaIndustrialBuildingMember
     
Total 7,119us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RaleighNorthCarolinaIndustrialBuildingMember
     
Accumulated Depreciation 1,142us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RaleighNorthCarolinaIndustrialBuildingMember
     
Net Real Estate 5,977us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RaleighNorthCarolinaIndustrialBuildingMember
     
Year Construction/ Improvements 1994      
Date Acquired Feb. 16, 2007      
Tulsa, Oklahoma Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 7,776us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TulsaOklahomaManufacturingBuildingMember
     
Buildings & Improvements, Initial Cost 14,057us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TulsaOklahomaManufacturingBuildingMember
     
Buildings & Improvements, Total cost 14,057us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TulsaOklahomaManufacturingBuildingMember
     
Total 14,057us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TulsaOklahomaManufacturingBuildingMember
     
Accumulated Depreciation 3,312us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TulsaOklahomaManufacturingBuildingMember
     
Net Real Estate 10,745us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TulsaOklahomaManufacturingBuildingMember
     
Year Construction/ Improvements 2004      
Date Acquired Mar. 01, 2007      
Hialeah, Florida Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 3,562us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HialeahFloridaIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 6,672us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HialeahFloridaIndustrialBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 685good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HialeahFloridaIndustrialBuildingMember
     
Land, Total cost 3,562us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HialeahFloridaIndustrialBuildingMember
     
Buildings & Improvements, Total cost 7,357us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HialeahFloridaIndustrialBuildingMember
     
Total 10,919us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HialeahFloridaIndustrialBuildingMember
     
Accumulated Depreciation 1,435us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HialeahFloridaIndustrialBuildingMember
     
Net Real Estate 9,484us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HialeahFloridaIndustrialBuildingMember
     
Year Construction/ Improvements 1956      
Year Construction/Improvements One 1992      
Date Acquired Mar. 09, 2007      
Tewksbury, Massachusetts Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 1,395us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TewksburyMassachusettsIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 8,893us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TewksburyMassachusettsIndustrialBuildingMember
     
Land, Total cost 1,395us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TewksburyMassachusettsIndustrialBuildingMember
     
Buildings & Improvements, Total cost 8,893us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TewksburyMassachusettsIndustrialBuildingMember
     
Total 10,288us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TewksburyMassachusettsIndustrialBuildingMember
     
Accumulated Depreciation 1,882us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TewksburyMassachusettsIndustrialBuildingMember
     
Net Real Estate 8,406us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TewksburyMassachusettsIndustrialBuildingMember
     
Year Construction/ Improvements 1985      
Year Construction/Improvements One 1989      
Date Acquired May 17, 2007      
Mason, Ohio Retail Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 4,555us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MasonOhioRetailBuildingMember
     
Land, Initial Cost 1,201us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MasonOhioRetailBuildingMember
     
Buildings & Improvements, Initial Cost 4,961us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MasonOhioRetailBuildingMember
     
Land, Total cost 1,201us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MasonOhioRetailBuildingMember
     
Buildings & Improvements, Total cost 4,961us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MasonOhioRetailBuildingMember
     
Total 6,162us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MasonOhioRetailBuildingMember
     
Accumulated Depreciation 969us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MasonOhioRetailBuildingMember
     
Net Real Estate 5,193us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MasonOhioRetailBuildingMember
     
Year Construction/ Improvements 2007      
Date Acquired Jul. 01, 2007      
Cicero, New York Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 3,964us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CiceroNewYorkIndustrialBuildingMember
     
Land, Initial Cost 299us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CiceroNewYorkIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 5,019us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CiceroNewYorkIndustrialBuildingMember
     
Land, Total cost 299us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CiceroNewYorkIndustrialBuildingMember
     
Buildings & Improvements, Total cost 5,019us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CiceroNewYorkIndustrialBuildingMember
     
Total 5,318us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CiceroNewYorkIndustrialBuildingMember
     
Accumulated Depreciation 942us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CiceroNewYorkIndustrialBuildingMember
     
Net Real Estate 4,376us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CiceroNewYorkIndustrialBuildingMember
     
Year Construction/ Improvements 2005      
Date Acquired Sep. 06, 2007      
Grand Rapids, Michigan Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 5,831us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_GrandRapidsMichiganOfficeBuildingMember
     
Land, Initial Cost 1,629us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_GrandRapidsMichiganOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 10,500us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_GrandRapidsMichiganOfficeBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 37good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_GrandRapidsMichiganOfficeBuildingMember
     
Land, Total cost 1,629us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_GrandRapidsMichiganOfficeBuildingMember
     
Buildings & Improvements, Total cost 10,537us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_GrandRapidsMichiganOfficeBuildingMember
     
Total 12,166us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_GrandRapidsMichiganOfficeBuildingMember
     
Accumulated Depreciation 2,055us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_GrandRapidsMichiganOfficeBuildingMember
     
Net Real Estate 10,111us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_GrandRapidsMichiganOfficeBuildingMember
     
Year Construction/ Improvements 2001      
Date Acquired Sep. 28, 2007      
Bollingbrook, Illinois Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 1,272us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BollingbrookIllinoisIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 5,003us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BollingbrookIllinoisIndustrialBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 475good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BollingbrookIllinoisIndustrialBuildingMember
     
Land, Total cost 1,272us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BollingbrookIllinoisIndustrialBuildingMember
     
Buildings & Improvements, Total cost 5,478us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BollingbrookIllinoisIndustrialBuildingMember
     
Total 6,750us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BollingbrookIllinoisIndustrialBuildingMember
     
Accumulated Depreciation 993us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BollingbrookIllinoisIndustrialBuildingMember
     
Net Real Estate 5,757us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BollingbrookIllinoisIndustrialBuildingMember
     
Year Construction/ Improvements 2002      
Date Acquired Sep. 28, 2007      
Decatur, Georgia Medical Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 784us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingOneMember
     
Buildings & Improvements, Initial Cost 3,245us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingOneMember
     
Land, Total cost 784us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingOneMember
     
Buildings & Improvements, Total cost 3,245us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingOneMember
     
Total 4,029us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingOneMember
     
Accumulated Depreciation 653us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingOneMember
     
Net Real Estate 3,376us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingOneMember
     
Year Construction/ Improvements 1989      
Date Acquired Dec. 13, 2007      
Decatur, Georgia Medical Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 205us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingTwoMember
     
Buildings & Improvements, Initial Cost 848us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingTwoMember
     
Land, Total cost 205us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingTwoMember
     
Buildings & Improvements, Total cost 848us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingTwoMember
     
Total 1,053us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingTwoMember
     
Accumulated Depreciation 171us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingTwoMember
     
Net Real Estate 882us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingTwoMember
     
Year Construction/ Improvements 1989      
Date Acquired Dec. 13, 2007      
Decatur, Georgia Medical Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 257us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingThreeMember
     
Buildings & Improvements, Initial Cost 1,064us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingThreeMember
     
Land, Total cost 257us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingThreeMember
     
Buildings & Improvements, Total cost 1,064us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingThreeMember
     
Total 1,321us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingThreeMember
     
Accumulated Depreciation 214us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingThreeMember
     
Net Real Estate 1,107us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DecaturGeorgiaOfficeBuildingThreeMember
     
Year Construction/ Improvements 1989      
Date Acquired Dec. 13, 2007      
Lawrenceville, Georgia Medical Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 679us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_LawrencevilleGeorgiaOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 2,809us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_LawrencevilleGeorgiaOfficeBuildingMember
     
Land, Total cost 679us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_LawrencevilleGeorgiaOfficeBuildingMember
     
Buildings & Improvements, Total cost 2,809us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_LawrencevilleGeorgiaOfficeBuildingMember
     
Total 3,488us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_LawrencevilleGeorgiaOfficeBuildingMember
     
Accumulated Depreciation 565us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_LawrencevilleGeorgiaOfficeBuildingMember
     
Net Real Estate 2,923us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_LawrencevilleGeorgiaOfficeBuildingMember
     
Year Construction/ Improvements 2005      
Date Acquired Dec. 13, 2007      
Snellville, Georgia Medical Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 176us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SnellvilleGeorgiaOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 729us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SnellvilleGeorgiaOfficeBuildingMember
     
Land, Total cost 176us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SnellvilleGeorgiaOfficeBuildingMember
     
Buildings & Improvements, Total cost 729us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SnellvilleGeorgiaOfficeBuildingMember
     
Total 905us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SnellvilleGeorgiaOfficeBuildingMember
     
Accumulated Depreciation 147us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SnellvilleGeorgiaOfficeBuildingMember
     
Net Real Estate 758us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SnellvilleGeorgiaOfficeBuildingMember
     
Year Construction/ Improvements 1986      
Date Acquired Dec. 13, 2007      
Covington, Georgia Medical Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 232us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CovingtonGeorgiaOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 959us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CovingtonGeorgiaOfficeBuildingMember
     
Land, Total cost 232us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CovingtonGeorgiaOfficeBuildingMember
     
Buildings & Improvements, Total cost 959us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CovingtonGeorgiaOfficeBuildingMember
     
Total 1,191us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CovingtonGeorgiaOfficeBuildingMember
     
Accumulated Depreciation 193us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CovingtonGeorgiaOfficeBuildingMember
     
Net Real Estate 998us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CovingtonGeorgiaOfficeBuildingMember
     
Year Construction/ Improvements 2000      
Date Acquired Dec. 13, 2007      
Cumming, Georgia Medical Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 3,145us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CummingGeorgiaOfficeBuildingMember
     
Land, Initial Cost 738us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CummingGeorgiaOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 3,055us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CummingGeorgiaOfficeBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 2,511good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CummingGeorgiaOfficeBuildingMember
     
Land, Total cost 738us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CummingGeorgiaOfficeBuildingMember
     
Buildings & Improvements, Total cost 5,566us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CummingGeorgiaOfficeBuildingMember
     
Total 6,304us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CummingGeorgiaOfficeBuildingMember
     
Accumulated Depreciation 615us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CummingGeorgiaOfficeBuildingMember
     
Net Real Estate 5,689us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CummingGeorgiaOfficeBuildingMember
     
Year Construction/ Improvements 2004      
Date Acquired Dec. 13, 2007      
Conyers, Georgia Medical Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 297us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ConyersGeorgiaOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 1,228us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ConyersGeorgiaOfficeBuildingMember
     
Land, Total cost 297us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ConyersGeorgiaOfficeBuildingMember
     
Buildings & Improvements, Total cost 1,228us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ConyersGeorgiaOfficeBuildingMember
     
Total 1,525us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ConyersGeorgiaOfficeBuildingMember
     
Accumulated Depreciation 247us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ConyersGeorgiaOfficeBuildingMember
     
Net Real Estate 1,278us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ConyersGeorgiaOfficeBuildingMember
     
Year Construction/ Improvements 1994      
Date Acquired Dec. 13, 2007      
Reading, Pennsylvania Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 3,983us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ReadingPennsylvaniaIndustrialBuildingMember
     
Land, Initial Cost 491us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ReadingPennsylvaniaIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 6,202us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ReadingPennsylvaniaIndustrialBuildingMember
     
Land, Total cost 491us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ReadingPennsylvaniaIndustrialBuildingMember
     
Buildings & Improvements, Total cost 6,202us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ReadingPennsylvaniaIndustrialBuildingMember
     
Total 6,693us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ReadingPennsylvaniaIndustrialBuildingMember
     
Accumulated Depreciation 1,104us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ReadingPennsylvaniaIndustrialBuildingMember
     
Net Real Estate 5,589us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ReadingPennsylvaniaIndustrialBuildingMember
     
Year Construction/ Improvements 2007      
Date Acquired Jan. 29, 2008      
Fridley, Minnesota Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 5,121us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FridleyMinnesotaOfficeBuildingMember
     
Land, Initial Cost 1,354us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FridleyMinnesotaOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 8,074us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FridleyMinnesotaOfficeBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 397good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FridleyMinnesotaOfficeBuildingMember
     
Land, Total cost 1,381us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FridleyMinnesotaOfficeBuildingMember
     
Buildings & Improvements, Total cost 8,444us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FridleyMinnesotaOfficeBuildingMember
     
Total 9,825us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FridleyMinnesotaOfficeBuildingMember
     
Accumulated Depreciation 1,816us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FridleyMinnesotaOfficeBuildingMember
     
Net Real Estate 8,009us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FridleyMinnesotaOfficeBuildingMember
     
Year Construction/ Improvements 1985      
Year Construction/Improvements One 2006      
Date Acquired Feb. 26, 2008      
Concord Township, Ohio Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 1,796us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ConcordTownshipOhioIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 11,154us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ConcordTownshipOhioIndustrialBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition (11)good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ConcordTownshipOhioIndustrialBuildingMember
     
Land, Total cost 1,785us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ConcordTownshipOhioIndustrialBuildingMember
     
Buildings & Improvements, Total cost 11,154us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ConcordTownshipOhioIndustrialBuildingMember
     
Total 12,939us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ConcordTownshipOhioIndustrialBuildingMember
     
Accumulated Depreciation 2,048us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ConcordTownshipOhioIndustrialBuildingMember
     
Net Real Estate 10,891us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ConcordTownshipOhioIndustrialBuildingMember
     
Year Construction/ Improvements 1957      
Year Construction/Improvements One 2008      
Date Acquired Mar. 31, 2008      
Pineville, North Carolina Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 2,315us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_PinevilleNorthCarolinaIndustrialBuildingMember
     
Land, Initial Cost 669us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_PinevilleNorthCarolinaIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 3,028us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_PinevilleNorthCarolinaIndustrialBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 6good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_PinevilleNorthCarolinaIndustrialBuildingMember
     
Land, Total cost 669us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_PinevilleNorthCarolinaIndustrialBuildingMember
     
Buildings & Improvements, Total cost 3,034us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_PinevilleNorthCarolinaIndustrialBuildingMember
     
Total 3,703us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_PinevilleNorthCarolinaIndustrialBuildingMember
     
Accumulated Depreciation 535us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_PinevilleNorthCarolinaIndustrialBuildingMember
     
Net Real Estate 3,168us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_PinevilleNorthCarolinaIndustrialBuildingMember
     
Year Construction/ Improvements 1985      
Date Acquired Apr. 30, 2008      
Marietta, Ohio Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 5,650us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MariettaOhioIndustrialBuildingMember
     
Land, Initial Cost 829us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MariettaOhioIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 6,607us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MariettaOhioIndustrialBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 209good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MariettaOhioIndustrialBuildingMember
     
Land, Total cost 829us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MariettaOhioIndustrialBuildingMember
     
Buildings & Improvements, Total cost 6,816us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MariettaOhioIndustrialBuildingMember
     
Total 7,645us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MariettaOhioIndustrialBuildingMember
     
Accumulated Depreciation 1,106us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MariettaOhioIndustrialBuildingMember
     
Net Real Estate 6,539us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MariettaOhioIndustrialBuildingMember
     
Year Construction/ Improvements 1992      
Year Construction/Improvements One 2007      
Date Acquired Aug. 29, 2008      
Chalfont, Pennsylvania Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 5,510us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChalfontPennsylvaniaIndustrialBuildingMember
     
Land, Initial Cost 1,249us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChalfontPennsylvaniaIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 6,420us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChalfontPennsylvaniaIndustrialBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 171good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChalfontPennsylvaniaIndustrialBuildingMember
     
Land, Total cost 1,249us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChalfontPennsylvaniaIndustrialBuildingMember
     
Buildings & Improvements, Total cost 6,591us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChalfontPennsylvaniaIndustrialBuildingMember
     
Total 7,840us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChalfontPennsylvaniaIndustrialBuildingMember
     
Accumulated Depreciation 1,270us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChalfontPennsylvaniaIndustrialBuildingMember
     
Net Real Estate 6,570us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ChalfontPennsylvaniaIndustrialBuildingMember
     
Year Construction/ Improvements 1987      
Date Acquired Aug. 29, 2008      
Orange City, Iowa Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 9,015us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_OrangeCityIowaOfficeAndWarehouseBuildingMember
     
Land, Initial Cost 258us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_OrangeCityIowaOfficeAndWarehouseBuildingMember
     
Buildings & Improvements, Initial Cost 5,861us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_OrangeCityIowaOfficeAndWarehouseBuildingMember
     
Land, Total cost 258us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_OrangeCityIowaOfficeAndWarehouseBuildingMember
     
Buildings & Improvements, Total cost 5,861us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_OrangeCityIowaOfficeAndWarehouseBuildingMember
     
Total 6,119us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_OrangeCityIowaOfficeAndWarehouseBuildingMember
     
Accumulated Depreciation 743us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_OrangeCityIowaOfficeAndWarehouseBuildingMember
     
Net Real Estate 5,376us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_OrangeCityIowaOfficeAndWarehouseBuildingMember
     
Year Construction/ Improvements 1990      
Date Acquired Dec. 15, 2010      
Hickory, North Carolina Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 6,697us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HickoryNorthCarolinaOfficeBuildingMember
     
Land, Initial Cost 1,163us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HickoryNorthCarolinaOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 6,605us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HickoryNorthCarolinaOfficeBuildingMember
     
Land, Total cost 1,163us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HickoryNorthCarolinaOfficeBuildingMember
     
Buildings & Improvements, Total cost 6,605us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HickoryNorthCarolinaOfficeBuildingMember
     
Total 7,768us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HickoryNorthCarolinaOfficeBuildingMember
     
Accumulated Depreciation 1,124us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HickoryNorthCarolinaOfficeBuildingMember
     
Net Real Estate 6,644us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_HickoryNorthCarolinaOfficeBuildingMember
     
Year Construction/ Improvements 2008      
Date Acquired Apr. 04, 2011      
Springfield, Missouri Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 10,977us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SpringfieldMissouriOfficeBuildingMember
     
Land, Initial Cost 1,700us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SpringfieldMissouriOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 12,038us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SpringfieldMissouriOfficeBuildingMember
     
Land, Total cost 1,700us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SpringfieldMissouriOfficeBuildingMember
     
Buildings & Improvements, Total cost 12,038us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SpringfieldMissouriOfficeBuildingMember
     
Total 13,738us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SpringfieldMissouriOfficeBuildingMember
     
Accumulated Depreciation 1,278us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SpringfieldMissouriOfficeBuildingMember
     
Net Real Estate 12,460us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SpringfieldMissouriOfficeBuildingMember
     
Year Construction/ Improvements 2006      
Date Acquired Jun. 20, 2011      
Boston Heights, Ohio Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 2,646us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BostonHeightsOhioOfficeBuildingMember
     
Land, Initial Cost 449us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BostonHeightsOhioOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 3,010us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BostonHeightsOhioOfficeBuildingMember
     
Land, Total cost 449us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BostonHeightsOhioOfficeBuildingMember
     
Buildings & Improvements, Total cost 3,010us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BostonHeightsOhioOfficeBuildingMember
     
Total 3,459us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BostonHeightsOhioOfficeBuildingMember
     
Accumulated Depreciation 427us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BostonHeightsOhioOfficeBuildingMember
     
Net Real Estate 3,032us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BostonHeightsOhioOfficeBuildingMember
     
Year Construction/ Improvements 2011      
Date Acquired Oct. 20, 2011      
Parsippany, New Jersey Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 6,799us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ParsippanyNewJerseyOfficeBuildingMember
     
Land, Initial Cost 1,696us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ParsippanyNewJerseyOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 7,077us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ParsippanyNewJerseyOfficeBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 81good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ParsippanyNewJerseyOfficeBuildingMember
     
Land, Total cost 1,696us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ParsippanyNewJerseyOfficeBuildingMember
     
Buildings & Improvements, Total cost 7,158us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ParsippanyNewJerseyOfficeBuildingMember
     
Total 8,854us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ParsippanyNewJerseyOfficeBuildingMember
     
Accumulated Depreciation 855us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ParsippanyNewJerseyOfficeBuildingMember
     
Net Real Estate 7,999us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ParsippanyNewJerseyOfficeBuildingMember
     
Year Construction/ Improvements 1984      
Date Acquired Oct. 28, 2011      
Dartmouth, Massachusetts Retail Location [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 4,049us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DartmouthMassachusettsRetailLocationMember
     
Buildings & Improvements, Initial Cost 4,236us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DartmouthMassachusettsRetailLocationMember
     
Buildings & Improvements, Total cost 4,236us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DartmouthMassachusettsRetailLocationMember
     
Total 4,236us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DartmouthMassachusettsRetailLocationMember
     
Accumulated Depreciation 368us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DartmouthMassachusettsRetailLocationMember
     
Net Real Estate 3,868us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DartmouthMassachusettsRetailLocationMember
     
Year Construction/ Improvements 2011      
Date Acquired Nov. 18, 2011      
Springfield, Missouri Retail Location [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 1,823us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SpringfieldMissouriRetailLocationMember
     
Buildings & Improvements, Initial Cost 2,275us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SpringfieldMissouriRetailLocationMember
     
Buildings & Improvements, Total cost 2,275us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SpringfieldMissouriRetailLocationMember
     
Total 2,275us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SpringfieldMissouriRetailLocationMember
     
Accumulated Depreciation 250us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SpringfieldMissouriRetailLocationMember
     
Net Real Estate 2,025us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_SpringfieldMissouriRetailLocationMember
     
Year Construction/ Improvements 2005      
Date Acquired Dec. 13, 2011      
Pittsburgh, Pennsylvania Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 2,757us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_PittsburghPennsylvaniaOfficeBuildingMember
     
Land, Initial Cost 281us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_PittsburghPennsylvaniaOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 3,205us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_PittsburghPennsylvaniaOfficeBuildingMember
     
Land, Total cost 281us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_PittsburghPennsylvaniaOfficeBuildingMember
     
Buildings & Improvements, Total cost 3,205us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_PittsburghPennsylvaniaOfficeBuildingMember
     
Total 3,486us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_PittsburghPennsylvaniaOfficeBuildingMember
     
Accumulated Depreciation 311us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_PittsburghPennsylvaniaOfficeBuildingMember
     
Net Real Estate 3,175us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_PittsburghPennsylvaniaOfficeBuildingMember
     
Year Construction/ Improvements 1968      
Date Acquired Dec. 28, 2011      
Ashburn, Virginia Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 7,223us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AshburnVirginiaOfficeBuildingMember
     
Land, Initial Cost 706us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AshburnVirginiaOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 7,858us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AshburnVirginiaOfficeBuildingMember
     
Land, Total cost 706us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AshburnVirginiaOfficeBuildingMember
     
Buildings & Improvements, Total cost 7,858us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AshburnVirginiaOfficeBuildingMember
     
Total 8,564us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AshburnVirginiaOfficeBuildingMember
     
Accumulated Depreciation 767us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AshburnVirginiaOfficeBuildingMember
     
Net Real Estate 7,797us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AshburnVirginiaOfficeBuildingMember
     
Year Construction/ Improvements 2002      
Date Acquired Jan. 25, 2012      
Ottumwa, Iowa Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 4,426us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_OttumwaIowaIndustrialMember
     
Land, Initial Cost 212us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_OttumwaIowaIndustrialMember
     
Buildings & Improvements, Initial Cost 5,072us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_OttumwaIowaIndustrialMember
     
Improvement Costs Capitalized Subsequent to Acquisition 287good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_OttumwaIowaIndustrialMember
     
Land, Total cost 212us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_OttumwaIowaIndustrialMember
     
Buildings & Improvements, Total cost 5,359us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_OttumwaIowaIndustrialMember
     
Total 5,571us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_OttumwaIowaIndustrialMember
     
Accumulated Depreciation 499us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_OttumwaIowaIndustrialMember
     
Net Real Estate 5,072us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_OttumwaIowaIndustrialMember
     
Year Construction/ Improvements 1970      
Date Acquired May 30, 2012      
New Albany, Ohio Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 9,066us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NewAlbanyOhioIndustrialMember
     
Land, Initial Cost 1,658us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NewAlbanyOhioIndustrialMember
     
Buildings & Improvements, Initial Cost 8,746us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NewAlbanyOhioIndustrialMember
     
Land, Total cost 1,658us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NewAlbanyOhioIndustrialMember
     
Buildings & Improvements, Total cost 8,746us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NewAlbanyOhioIndustrialMember
     
Total 10,404us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NewAlbanyOhioIndustrialMember
     
Accumulated Depreciation 831us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NewAlbanyOhioIndustrialMember
     
Net Real Estate 9,573us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NewAlbanyOhioIndustrialMember
     
Year Construction/ Improvements 2007      
Date Acquired Jun. 05, 2012      
Columbus, Georgia Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 4,507us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusGeorgiaOfficeMember
     
Land, Initial Cost 1,378us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusGeorgiaOfficeMember
     
Buildings & Improvements, Initial Cost 4,520us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusGeorgiaOfficeMember
     
Land, Total cost 1,378us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusGeorgiaOfficeMember
     
Buildings & Improvements, Total cost 4,520us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusGeorgiaOfficeMember
     
Total 5,898us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusGeorgiaOfficeMember
     
Accumulated Depreciation 471us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusGeorgiaOfficeMember
     
Net Real Estate 5,427us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusGeorgiaOfficeMember
     
Year Construction/ Improvements 2012      
Date Acquired Jun. 21, 2012      
Columbus, Ohio Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 2,845us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioOfficeMember
     
Land, Initial Cost 542us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioOfficeMember
     
Buildings & Improvements, Initial Cost 2,453us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioOfficeMember
     
Improvement Costs Capitalized Subsequent to Acquisition 11good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioOfficeMember
     
Land, Total cost 542us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioOfficeMember
     
Buildings & Improvements, Total cost 2,464us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioOfficeMember
     
Total 3,006us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioOfficeMember
     
Accumulated Depreciation 287us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioOfficeMember
     
Net Real Estate 2,719us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioOfficeMember
     
Year Construction/ Improvements 1981      
Date Acquired Jun. 28, 2012      
Jupiter, Florida Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 10,252us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_JupiterFloridaOfficeMember
     
Land, Initial Cost 1,160us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_JupiterFloridaOfficeMember
     
Buildings & Improvements, Initial Cost 11,994us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_JupiterFloridaOfficeMember
     
Land, Total cost 1,160us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_JupiterFloridaOfficeMember
     
Buildings & Improvements, Total cost 11,994us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_JupiterFloridaOfficeMember
     
Total 13,154us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_JupiterFloridaOfficeMember
     
Accumulated Depreciation 827us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_JupiterFloridaOfficeMember
     
Net Real Estate 12,327us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_JupiterFloridaOfficeMember
     
Year Construction/ Improvements 2011      
Date Acquired Sep. 26, 2012      
Fort Worth, Texas Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 13,567us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FortWorthTexasOfficeMember
     
Land, Initial Cost 963us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FortWorthTexasOfficeMember
     
Buildings & Improvements, Initial Cost 15,647us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FortWorthTexasOfficeMember
     
Land, Total cost 963us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FortWorthTexasOfficeMember
     
Buildings & Improvements, Total cost 15,647us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FortWorthTexasOfficeMember
     
Total 16,610us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FortWorthTexasOfficeMember
     
Accumulated Depreciation 1,022us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FortWorthTexasOfficeMember
     
Net Real Estate 15,588us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_FortWorthTexasOfficeMember
     
Year Construction/ Improvements 2005      
Date Acquired Nov. 08, 2012      
Columbia, South Carolina Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 18,067us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbiaSouthCarolinaOfficeMember
     
Land, Initial Cost 1,905us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbiaSouthCarolinaOfficeMember
     
Buildings & Improvements, Initial Cost 20,648us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbiaSouthCarolinaOfficeMember
     
Land, Total cost 1,905us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbiaSouthCarolinaOfficeMember
     
Buildings & Improvements, Total cost 20,648us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbiaSouthCarolinaOfficeMember
     
Total 22,553us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbiaSouthCarolinaOfficeMember
     
Accumulated Depreciation 1,864us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbiaSouthCarolinaOfficeMember
     
Net Real Estate 20,689us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbiaSouthCarolinaOfficeMember
     
Year Construction/ Improvements 2010      
Date Acquired Nov. 21, 2012      
Egg Harbor, New Jersey Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 3,551us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EggHarborNewJerseyOfficeBuildingMember
     
Land, Initial Cost 1,627us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EggHarborNewJerseyOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 3,017us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EggHarborNewJerseyOfficeBuildingMember
     
Improvement Costs Capitalized Subsequent to Acquisition 236good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EggHarborNewJerseyOfficeBuildingMember
     
Land, Total cost 1,627us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EggHarborNewJerseyOfficeBuildingMember
     
Buildings & Improvements, Total cost 3,253us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EggHarborNewJerseyOfficeBuildingMember
     
Total 4,880us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EggHarborNewJerseyOfficeBuildingMember
     
Accumulated Depreciation 201us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EggHarborNewJerseyOfficeBuildingMember
     
Net Real Estate 4,679us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EggHarborNewJerseyOfficeBuildingMember
     
Year Construction/ Improvements 1985      
Date Acquired Mar. 28, 2013      
Vance, Alabama Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 457us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_VanceAlabamaIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 10,529us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_VanceAlabamaIndustrialBuildingMember
     
Land, Total cost 457us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_VanceAlabamaIndustrialBuildingMember
     
Buildings & Improvements, Total cost 10,529us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_VanceAlabamaIndustrialBuildingMember
     
Total 10,986us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_VanceAlabamaIndustrialBuildingMember
     
Accumulated Depreciation 604us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_VanceAlabamaIndustrialBuildingMember
     
Net Real Estate 10,382us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_VanceAlabamaIndustrialBuildingMember
     
Year Construction/ Improvements 2013      
Date Acquired May 09, 2013      
Blaine, Minnesota Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 8,045us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BlaineMinnesotaOfficeBuildingMember
     
Land, Initial Cost 1,060us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BlaineMinnesotaOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 10,519us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BlaineMinnesotaOfficeBuildingMember
     
Land, Total cost 1,060us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BlaineMinnesotaOfficeBuildingMember
     
Buildings & Improvements, Total cost 10,519us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BlaineMinnesotaOfficeBuildingMember
     
Total 11,579us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BlaineMinnesotaOfficeBuildingMember
     
Accumulated Depreciation 748us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BlaineMinnesotaOfficeBuildingMember
     
Net Real Estate 10,831us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_BlaineMinnesotaOfficeBuildingMember
     
Year Construction/ Improvements 2009      
Date Acquired May 10, 2013      
Austin, Texas Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 34,567us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AustinTexasOfficeBuildingOneMember
     
Land, Initial Cost 2,330us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AustinTexasOfficeBuildingOneMember
     
Buildings & Improvements, Initial Cost 44,021us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AustinTexasOfficeBuildingOneMember
     
Improvement Costs Capitalized Subsequent to Acquisition 122good_RealEstateCostsAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AustinTexasOfficeBuildingOneMember
     
Land, Total cost 2,330us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AustinTexasOfficeBuildingOneMember
     
Buildings & Improvements, Total cost 44,143us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AustinTexasOfficeBuildingOneMember
     
Total 46,473us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AustinTexasOfficeBuildingOneMember
     
Accumulated Depreciation 3,071us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AustinTexasOfficeBuildingOneMember
     
Net Real Estate 43,402us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AustinTexasOfficeBuildingOneMember
     
Year Construction/ Improvements 1999      
Date Acquired Jul. 09, 2013      
Allen, Texas Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 8,704us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AllenTexasOfficeBuildingMember
     
Land, Initial Cost 2,699us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AllenTexasOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 7,945us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AllenTexasOfficeBuildingMember
     
Land, Total cost 2,699us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AllenTexasOfficeBuildingMember
     
Buildings & Improvements, Total cost 7,945us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AllenTexasOfficeBuildingMember
     
Total 10,644us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AllenTexasOfficeBuildingMember
     
Accumulated Depreciation 602us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AllenTexasOfficeBuildingMember
     
Net Real Estate 10,042us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AllenTexasOfficeBuildingMember
     
Year Construction/ Improvements 1998      
Date Acquired Jul. 10, 2013      
Englewood, Colorado Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 11,315us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EnglewoodColoradoOfficeBuildingMember
     
Land, Initial Cost 1,503us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EnglewoodColoradoOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 11,739us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EnglewoodColoradoOfficeBuildingMember
     
Land, Total cost 1,503us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EnglewoodColoradoOfficeBuildingMember
     
Buildings & Improvements, Total cost 11,739us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EnglewoodColoradoOfficeBuildingMember
     
Total 13,242us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EnglewoodColoradoOfficeBuildingMember
     
Accumulated Depreciation 546us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EnglewoodColoradoOfficeBuildingMember
     
Net Real Estate 12,696us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_EnglewoodColoradoOfficeBuildingMember
     
Year Construction/ Improvements 2008      
Date Acquired Dec. 11, 2013      
Novi, Michigan Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 4,297us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NoviMichiganIndustrialBuildingMember
     
Land, Initial Cost 352us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NoviMichiganIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 5,626us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NoviMichiganIndustrialBuildingMember
     
Land, Total cost 352us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NoviMichiganIndustrialBuildingMember
     
Buildings & Improvements, Total cost 5,626us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NoviMichiganIndustrialBuildingMember
     
Total 5,978us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NoviMichiganIndustrialBuildingMember
     
Accumulated Depreciation 197us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NoviMichiganIndustrialBuildingMember
     
Net Real Estate 5,781us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_NoviMichiganIndustrialBuildingMember
     
Year Construction/ Improvements 1988      
Date Acquired Dec. 27, 2013      
Allen, Texas Retail Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 3,417us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AllenTexasRetailBuildingMember
     
Land, Initial Cost 874us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AllenTexasRetailBuildingMember
     
Buildings & Improvements, Initial Cost 3,634us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AllenTexasRetailBuildingMember
     
Land, Total cost 874us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AllenTexasRetailBuildingMember
     
Buildings & Improvements, Total cost 3,634us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AllenTexasRetailBuildingMember
     
Total 4,508us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AllenTexasRetailBuildingMember
     
Accumulated Depreciation 95us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AllenTexasRetailBuildingMember
     
Net Real Estate 4,413us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AllenTexasRetailBuildingMember
     
Year Construction/ Improvements 2004      
Date Acquired Mar. 27, 2014      
Colleyville, Texas Retail Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 2,797us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColleyvilleTexasRetailBuildingMember
     
Land, Initial Cost 1,277us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColleyvilleTexasRetailBuildingMember
     
Buildings & Improvements, Initial Cost 2,424us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColleyvilleTexasRetailBuildingMember
     
Land, Total cost 1,277us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColleyvilleTexasRetailBuildingMember
     
Buildings & Improvements, Total cost 2,424us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColleyvilleTexasRetailBuildingMember
     
Total 3,701us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColleyvilleTexasRetailBuildingMember
     
Accumulated Depreciation 72us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColleyvilleTexasRetailBuildingMember
     
Net Real Estate 3,629us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColleyvilleTexasRetailBuildingMember
     
Year Construction/ Improvements 2000      
Date Acquired Mar. 27, 2014      
Rancho Cordova, California Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 4,935us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RanchoCordovaCaliforniaOfficeBuildingMember
     
Land, Initial Cost 752us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RanchoCordovaCaliforniaOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 6,176us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RanchoCordovaCaliforniaOfficeBuildingMember
     
Land, Total cost 752us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RanchoCordovaCaliforniaOfficeBuildingMember
     
Buildings & Improvements, Total cost 6,176us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RanchoCordovaCaliforniaOfficeBuildingMember
     
Total 6,928us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RanchoCordovaCaliforniaOfficeBuildingMember
     
Accumulated Depreciation 150us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RanchoCordovaCaliforniaOfficeBuildingMember
     
Net Real Estate 6,778us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_RanchoCordovaCaliforniaOfficeBuildingMember
     
Year Construction/ Improvements 1986      
Date Acquired Apr. 22, 2014      
Coppell, Texas Retail Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 3,767us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CoppellTexasRetailBuildingMember
     
Land, Initial Cost 1,448us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CoppellTexasRetailBuildingMember
     
Buildings & Improvements, Initial Cost 3,349us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CoppellTexasRetailBuildingMember
     
Land, Total cost 1,448us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CoppellTexasRetailBuildingMember
     
Buildings & Improvements, Total cost 3,349us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CoppellTexasRetailBuildingMember
     
Total 4,797us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CoppellTexasRetailBuildingMember
     
Accumulated Depreciation 74us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CoppellTexasRetailBuildingMember
     
Net Real Estate 4,723us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_CoppellTexasRetailBuildingMember
     
Year Construction/ Improvements 2005      
Date Acquired May 08, 2014      
Columbus, Ohio Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 990us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 8,017us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioOfficeBuildingMember
     
Land, Total cost 990us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioOfficeBuildingMember
     
Buildings & Improvements, Total cost 8,017us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioOfficeBuildingMember
     
Total 9,007us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioOfficeBuildingMember
     
Accumulated Depreciation 266us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioOfficeBuildingMember
     
Net Real Estate 8,741us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_ColumbusOhioOfficeBuildingMember
     
Year Construction/ Improvements 1986      
Date Acquired May 13, 2014      
Taylor, Pennsylvania Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 22,600us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TaylorPennsylvaniaIndustrialBuildingMember
     
Land, Initial Cost 3,102us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TaylorPennsylvaniaIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 25,405us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TaylorPennsylvaniaIndustrialBuildingMember
     
Land, Total cost 3,102us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TaylorPennsylvaniaIndustrialBuildingMember
     
Buildings & Improvements, Total cost 25,405us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TaylorPennsylvaniaIndustrialBuildingMember
     
Total 28,507us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TaylorPennsylvaniaIndustrialBuildingMember
     
Accumulated Depreciation 451us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TaylorPennsylvaniaIndustrialBuildingMember
     
Net Real Estate 28,056us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_TaylorPennsylvaniaIndustrialBuildingMember
     
Year Construction/ Improvements 2000      
Year Construction/Improvements One 2006      
Date Acquired Jun. 09, 2014      
Aurora, Colorado Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 2,882us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AuroraColoradoIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 4,013us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AuroraColoradoIndustrialBuildingMember
     
Land, Total cost 2,882us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AuroraColoradoIndustrialBuildingMember
     
Buildings & Improvements, Total cost 4,013us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AuroraColoradoIndustrialBuildingMember
     
Total 6,895us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AuroraColoradoIndustrialBuildingMember
     
Accumulated Depreciation 82us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AuroraColoradoIndustrialBuildingMember
     
Net Real Estate 6,813us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_AuroraColoradoIndustrialBuildingMember
     
Year Construction/ Improvements 1983      
Date Acquired Jul. 01, 2014      
Indianapolis, Indiana Office Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 6,100us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_IndianapolisIndianaOfficeBuildingMember
     
Land, Initial Cost 502us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_IndianapolisIndianaOfficeBuildingMember
     
Buildings & Improvements, Initial Cost 6,490us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_IndianapolisIndianaOfficeBuildingMember
     
Land, Total cost 502us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_IndianapolisIndianaOfficeBuildingMember
     
Buildings & Improvements, Total cost 6,490us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_IndianapolisIndianaOfficeBuildingMember
     
Total 6,992us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_IndianapolisIndianaOfficeBuildingMember
     
Accumulated Depreciation 99us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_IndianapolisIndianaOfficeBuildingMember
     
Net Real Estate 6,893us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_IndianapolisIndianaOfficeBuildingMember
     
Year Construction/ Improvements 1981      
Year Construction/Improvements One 2014      
Date Acquired Sep. 03, 2014      
Denver, Colorado Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Land, Initial Cost 1,621us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DenverColoradoIndustrialBuildingMember
     
Buildings & Improvements, Initial Cost 7,314us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DenverColoradoIndustrialBuildingMember
     
Land, Total cost 1,621us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DenverColoradoIndustrialBuildingMember
     
Buildings & Improvements, Total cost 7,314us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DenverColoradoIndustrialBuildingMember
     
Total 8,935us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DenverColoradoIndustrialBuildingMember
     
Accumulated Depreciation 46us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DenverColoradoIndustrialBuildingMember
     
Net Real Estate 8,889us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_DenverColoradoIndustrialBuildingMember
     
Year Construction/ Improvements 1985      
Date Acquired Oct. 31, 2014      
Monroe, Michigan Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 10,839us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MonroeMichiganIndustrialBuildingOneMember
     
Land, Initial Cost 658us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MonroeMichiganIndustrialBuildingOneMember
     
Buildings & Improvements, Initial Cost 14,607us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MonroeMichiganIndustrialBuildingOneMember
     
Land, Total cost 658us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MonroeMichiganIndustrialBuildingOneMember
     
Buildings & Improvements, Total cost 14,607us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MonroeMichiganIndustrialBuildingOneMember
     
Total 15,265us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MonroeMichiganIndustrialBuildingOneMember
     
Accumulated Depreciation 11us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MonroeMichiganIndustrialBuildingOneMember
     
Net Real Estate 15,254us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MonroeMichiganIndustrialBuildingOneMember
     
Year Construction/ Improvements 2004      
Date Acquired Dec. 23, 2014      
Monroe, Michigan Industrial Building [Member]        
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances, Initial Cost 7,587us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MonroeMichiganIndustrialBuildingTwoMember
     
Land, Initial Cost 460us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MonroeMichiganIndustrialBuildingTwoMember
     
Buildings & Improvements, Initial Cost 10,225us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MonroeMichiganIndustrialBuildingTwoMember
     
Land, Total cost 460us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MonroeMichiganIndustrialBuildingTwoMember
     
Buildings & Improvements, Total cost 10,225us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MonroeMichiganIndustrialBuildingTwoMember
     
Total 10,685us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MonroeMichiganIndustrialBuildingTwoMember
     
Accumulated Depreciation 7us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MonroeMichiganIndustrialBuildingTwoMember
     
Net Real Estate $ 10,678us-gaap_SECScheduleIIIRealEstateInvestmentPropertyNet
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= good_MonroeMichiganIndustrialBuildingTwoMember
     
Year Construction/ Improvements 2004      
Date Acquired Dec. 23, 2014