|
Stockholders' Equity - Summary of Changes in Stockholders' Equity (Detail)
|
1 Months Ended |
12 Months Ended |
|
Feb. 29, 2012
|
Dec. 31, 2014
|
Dec. 31, 2013
|
Dec. 31, 2012
|
| Series C Preferred Stock [Member] |
|
|
|
|
| Dividends Payable [Line Items] |
|
|
|
|
| Preferred stock |
7.125%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesCPreferredStockMember
|
|
|
|
| Ordinary Income [Member] | Common Stock [Member] |
|
|
|
|
| Dividends Payable [Line Items] |
|
|
|
|
| Common stock |
|
0.00%good_CommonStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonStockMember
/ us-gaap_StatementEquityComponentsAxis
= good_OrdinaryIncomeMember
|
18.32962%good_CommonStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonStockMember
/ us-gaap_StatementEquityComponentsAxis
= good_OrdinaryIncomeMember
|
0.00%good_CommonStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonStockMember
/ us-gaap_StatementEquityComponentsAxis
= good_OrdinaryIncomeMember
|
| Ordinary Income [Member] | Senior Common Stock [Member] |
|
|
|
|
| Dividends Payable [Line Items] |
|
|
|
|
| Common stock |
|
0.00%good_CommonStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= good_SeniorCommonStockMember
/ us-gaap_StatementEquityComponentsAxis
= good_OrdinaryIncomeMember
|
100.00%good_CommonStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= good_SeniorCommonStockMember
/ us-gaap_StatementEquityComponentsAxis
= good_OrdinaryIncomeMember
|
0.00%good_CommonStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= good_SeniorCommonStockMember
/ us-gaap_StatementEquityComponentsAxis
= good_OrdinaryIncomeMember
|
| Ordinary Income [Member] | Series A Preferred Stock [Member] |
|
|
|
|
| Dividends Payable [Line Items] |
|
|
|
|
| Preferred stock |
|
24.10732%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredClassAMember
/ us-gaap_StatementEquityComponentsAxis
= good_OrdinaryIncomeMember
|
100.00%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredClassAMember
/ us-gaap_StatementEquityComponentsAxis
= good_OrdinaryIncomeMember
|
91.7083%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredClassAMember
/ us-gaap_StatementEquityComponentsAxis
= good_OrdinaryIncomeMember
|
| Ordinary Income [Member] | Series B Preferred Stock [Member] |
|
|
|
|
| Dividends Payable [Line Items] |
|
|
|
|
| Preferred stock |
|
24.10732%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredClassBMember
/ us-gaap_StatementEquityComponentsAxis
= good_OrdinaryIncomeMember
|
100.00%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredClassBMember
/ us-gaap_StatementEquityComponentsAxis
= good_OrdinaryIncomeMember
|
91.7083%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredClassBMember
/ us-gaap_StatementEquityComponentsAxis
= good_OrdinaryIncomeMember
|
| Ordinary Income [Member] | Series C Preferred Stock [Member] |
|
|
|
|
| Dividends Payable [Line Items] |
|
|
|
|
| Preferred stock |
|
24.10732%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesCPreferredStockMember
/ us-gaap_StatementEquityComponentsAxis
= good_OrdinaryIncomeMember
|
100.00%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesCPreferredStockMember
/ us-gaap_StatementEquityComponentsAxis
= good_OrdinaryIncomeMember
|
91.7083%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesCPreferredStockMember
/ us-gaap_StatementEquityComponentsAxis
= good_OrdinaryIncomeMember
|
| Return of Capital [Member] | Common Stock [Member] |
|
|
|
|
| Dividends Payable [Line Items] |
|
|
|
|
| Common stock |
|
100.00%good_CommonStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonStockMember
/ us-gaap_StatementEquityComponentsAxis
= good_ReturnOfCapitalMember
|
81.67038%good_CommonStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonStockMember
/ us-gaap_StatementEquityComponentsAxis
= good_ReturnOfCapitalMember
|
100.00%good_CommonStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonStockMember
/ us-gaap_StatementEquityComponentsAxis
= good_ReturnOfCapitalMember
|
| Return of Capital [Member] | Senior Common Stock [Member] |
|
|
|
|
| Dividends Payable [Line Items] |
|
|
|
|
| Common stock |
|
100.00%good_CommonStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= good_SeniorCommonStockMember
/ us-gaap_StatementEquityComponentsAxis
= good_ReturnOfCapitalMember
|
0.00%good_CommonStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= good_SeniorCommonStockMember
/ us-gaap_StatementEquityComponentsAxis
= good_ReturnOfCapitalMember
|
100.00%good_CommonStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= good_SeniorCommonStockMember
/ us-gaap_StatementEquityComponentsAxis
= good_ReturnOfCapitalMember
|
| Return of Capital [Member] | Series A Preferred Stock [Member] |
|
|
|
|
| Dividends Payable [Line Items] |
|
|
|
|
| Preferred stock |
|
75.89268%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredClassAMember
/ us-gaap_StatementEquityComponentsAxis
= good_ReturnOfCapitalMember
|
0.00%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredClassAMember
/ us-gaap_StatementEquityComponentsAxis
= good_ReturnOfCapitalMember
|
8.2917%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredClassAMember
/ us-gaap_StatementEquityComponentsAxis
= good_ReturnOfCapitalMember
|
| Return of Capital [Member] | Series B Preferred Stock [Member] |
|
|
|
|
| Dividends Payable [Line Items] |
|
|
|
|
| Preferred stock |
|
75.89268%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredClassBMember
/ us-gaap_StatementEquityComponentsAxis
= good_ReturnOfCapitalMember
|
0.00%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredClassBMember
/ us-gaap_StatementEquityComponentsAxis
= good_ReturnOfCapitalMember
|
8.2917%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredClassBMember
/ us-gaap_StatementEquityComponentsAxis
= good_ReturnOfCapitalMember
|
| Return of Capital [Member] | Series C Preferred Stock [Member] |
|
|
|
|
| Dividends Payable [Line Items] |
|
|
|
|
| Preferred stock |
|
75.89268%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesCPreferredStockMember
/ us-gaap_StatementEquityComponentsAxis
= good_ReturnOfCapitalMember
|
0.00%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesCPreferredStockMember
/ us-gaap_StatementEquityComponentsAxis
= good_ReturnOfCapitalMember
|
8.2917%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesCPreferredStockMember
/ us-gaap_StatementEquityComponentsAxis
= good_ReturnOfCapitalMember
|