Quarterly report pursuant to Section 13 or 15(d)

Mortgage Notes Payable and Line of Credit - Company's Mortgage Notes Payable and Line of Credit (Detail)

v2.4.1.9
Mortgage Notes Payable and Line of Credit - Company's Mortgage Notes Payable and Line of Credit (Detail) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Property
Dec. 31, 2014
Debt Instrument [Line Items]    
Encumbered properties 96good_NumberOfExistingEncumberedProperties  
Carrying value $ 510,348us-gaap_LongTermDebt $ 502,599us-gaap_LongTermDebt
Stated Interest Rates One month LIBOR was approximately 0.18%.  
Variable Rate Line of Credit [Member]    
Debt Instrument [Line Items]    
Encumbered properties 18good_NumberOfExistingEncumberedProperties
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember 		 
Carrying value 41,300us-gaap_LongTermDebt
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember 		43,300us-gaap_LongTermDebt
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
Stated Interest Rates LIBOR + 2.75%  
Libor rate 2.75%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember 		 
Scheduled Maturity Dates Aug. 01, 2017  
Premiums and Discounts (Net) [Member]    
Debt Instrument [Line Items]    
Carrying value 630us-gaap_LongTermDebt
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_PremiumsReceivableMember 		707us-gaap_LongTermDebt
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_PremiumsReceivableMember
Fixed Rate Mortgage Loans [Member]    
Debt Instrument [Line Items]    
Encumbered properties 74good_NumberOfExistingEncumberedProperties
/ us-gaap_DebtInstrumentAxis
= good_FixedRateMortgageLoansMember 		 
Carrying value 460,218us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= good_FixedRateMortgageLoansMember 		450,392us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= good_FixedRateMortgageLoansMember
Variable Rate Mortgage Loans [Member]    
Debt Instrument [Line Items]    
Encumbered properties 4good_NumberOfExistingEncumberedProperties
/ us-gaap_DebtInstrumentAxis
= good_VariableRateMortgagesMember 		 
Carrying value 8,200us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= good_VariableRateMortgagesMember 		8,200us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= good_VariableRateMortgagesMember
Stated Interest Rates LIBOR + 2.15%  
Libor rate 2.15%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_DebtInstrumentAxis
= good_VariableRateMortgagesMember 		 
Scheduled Maturity Dates Dec. 01, 2016  
Mortgage Notes Payable [Member]    
Debt Instrument [Line Items]    
Encumbered properties 78good_NumberOfExistingEncumberedProperties
/ us-gaap_DebtInstrumentAxis
= good_MortgageNotesPayableMember 		 
Carrying value $ 469,048us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= good_MortgageNotesPayableMember 		$ 459,299us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= good_MortgageNotesPayableMember