Annual report pursuant to Section 13 and 15(d)

Real Estate and Intangible Assets - Summary of Estimated Aggregate Rental Income (Detail)

v2.4.1.9
Real Estate and Intangible Assets - Summary of Estimated Aggregate Rental Income (Detail) (Above and Below Market Leases [Member], USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Above and Below Market Leases [Member]
 
Schedule Of Operating Leases Future Minimum Payments Receivable [Line Items]  
2015 $ 557us-gaap_OperatingLeasesFutureMinimumPaymentsReceivableCurrent
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= good_AboveAndBelowMarketLeasesMember
2016 438us-gaap_OperatingLeasesFutureMinimumPaymentsReceivableInTwoYears
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= good_AboveAndBelowMarketLeasesMember
2017 432us-gaap_OperatingLeasesFutureMinimumPaymentsReceivableInThreeYears
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= good_AboveAndBelowMarketLeasesMember
2018 432us-gaap_OperatingLeasesFutureMinimumPaymentsReceivableInFourYears
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= good_AboveAndBelowMarketLeasesMember
2019 432us-gaap_OperatingLeasesFutureMinimumPaymentsReceivableInFiveYears
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= good_AboveAndBelowMarketLeasesMember
Thereafter 4,374us-gaap_OperatingLeasesFutureMinimumPaymentsReceivableThereafter
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= good_AboveAndBelowMarketLeasesMember
Total $ 6,665us-gaap_OperatingLeasesFutureMinimumPaymentsReceivable
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= good_AboveAndBelowMarketLeasesMember