Quarterly report pursuant to Section 13 or 15(d)

Mortgage Notes Payable and Line of Credit - Schedule of Principal Payments of Mortgage Notes Payable (Detail)

v2.4.1.9
Mortgage Notes Payable and Line of Credit - Schedule of Principal Payments of Mortgage Notes Payable (Detail) (Mortgage Notes Payable [Member], USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Mortgage Notes Payable [Member]
 
Debt Instrument [Line Items]  
Nine Months ending December 31, 2015 $ 40,343us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear
/ us-gaap_DebtInstrumentAxis
= good_MortgageNotesPayableMember
2016 96,812us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths
/ us-gaap_DebtInstrumentAxis
= good_MortgageNotesPayableMember
2017 67,924us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo
/ us-gaap_DebtInstrumentAxis
= good_MortgageNotesPayableMember
2018 20,543us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree
/ us-gaap_DebtInstrumentAxis
= good_MortgageNotesPayableMember
2019 35,235us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour
/ us-gaap_DebtInstrumentAxis
= good_MortgageNotesPayableMember
2020 7,307us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive
/ us-gaap_DebtInstrumentAxis
= good_MortgageNotesPayableMember
Thereafter 200,254good_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearSix
/ us-gaap_DebtInstrumentAxis
= good_MortgageNotesPayableMember
Total Mortgage Notes Payable $ 468,418us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= good_MortgageNotesPayableMember