Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Dividends Declared (Detail)

v2.4.1.9
Stockholders' Equity - Dividends Declared (Detail) (USD $)
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Common Stock [Member]    
Dividends Payable [Line Items]    
Common Stock, distributions declared per share $ 0.375us-gaap_CommonStockDividendsPerShareDeclared
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember
$ 0.375us-gaap_CommonStockDividendsPerShareDeclared
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember
Senior Common Stock [Member]    
Dividends Payable [Line Items]    
Common Stock, distributions declared per share $ 0.2625us-gaap_CommonStockDividendsPerShareDeclared
/ us-gaap_StatementClassOfStockAxis
= good_SeniorCommonStockMember
$ 0.2625us-gaap_CommonStockDividendsPerShareDeclared
/ us-gaap_StatementClassOfStockAxis
= good_SeniorCommonStockMember
Series A Preferred Stock [Member]    
Dividends Payable [Line Items]    
Preferred Stock, distributions declared per share $ 0.4843749us-gaap_PreferredStockDividendsPerShareDeclared
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesAPreferredStockMember
$ 0.4843749us-gaap_PreferredStockDividendsPerShareDeclared
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesAPreferredStockMember
Series B Preferred Stock [Member]    
Dividends Payable [Line Items]    
Preferred Stock, distributions declared per share $ 0.4688us-gaap_PreferredStockDividendsPerShareDeclared
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesBPreferredStockMember
$ 0.4688us-gaap_PreferredStockDividendsPerShareDeclared
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesBPreferredStockMember
Series C Preferred Stock [Member]    
Dividends Payable [Line Items]    
Preferred Stock, distributions declared per share $ 0.4453us-gaap_PreferredStockDividendsPerShareDeclared
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesCPreferredStockMember
$ 0.4453us-gaap_PreferredStockDividendsPerShareDeclared
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesCPreferredStockMember