XML 35 R23.htm IDEA: XBRL DOCUMENT
v3.20.2

Organization, Basis of Presentation and Significant Accounting Policies - Additional Information (Details) - tenant | Sep. 30, 2020 | Apr. 30, 2020
--- | --- | ---
Organization, Consolidation and Presentation of Financial Statements [Abstract] |  |
Rent obligations deferred, number of tenants | 3 |
Rent obligations deferred (as percent) | 2.00% | 2.00%

X
- Definition Rent Obligations Deferred, Number of Tenants + References No definition available. + Details
Name: | good_RentObligationsDeferredNumberOfTenants
Namespace Prefix: | good_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Rent Obligations Deferred, Percentage + References No definition available. + Details
Name: | good_RentObligationsDeferredPercentage
Namespace Prefix: | good_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration