XML 276 R60.htm IDEA: XBRL DOCUMENT
v3.20.4

Schedule III - Real Estate and Accumulated Depreciation - Change in Balance of Real Estate (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward] |  |  |
Balance at beginning of period | $ 1,064,389 | $ 949,822 | $ 906,850
Additions: |  |  |
Acquisitions during period | 111,049 | 108,972 | 53,432
Improvements | 11,696 | 10,580 | 4,824
Deductions: |  |  |
Dispositions during period | (43,383) | (3,172) | (15,284)
Impairments during period | (3,546) | (1,813) | 0
Balance at end of period | $ 1,140,205 | $ 1,064,389 | $ 949,822

X
- Definition Additions. + References No definition available. + Details
Name: | good_AdditionsAbstract
Namespace Prefix: | good_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Asset Impairment Charges, Excluding Intangible Assets + References No definition available. + Details
Name: | good_AssetImpairmentChargesExcludingIntangibleAssets
Namespace Prefix: | good_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Deductions. + References No definition available. + Details
Name: | good_DeductionsAbstract
Namespace Prefix: | good_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of real estate investments sold for entities with a substantial portion of business acquiring and holding investment real estate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 970 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Footnote 4)) -URI http://asc.fasb.org/extlink&oid=120402810&loc=d3e638233-123024 + Details
Name: | us-gaap_RealEstateCostOfRealEstateSold
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount, before accumulated depreciation, of real estate investment by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate. Excludes real estate not held as investment or interest. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 970 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Column E)) -URI http://asc.fasb.org/extlink&oid=120402810&loc=d3e638233-123024 + Details
Name: | us-gaap_RealEstateGrossAtCarryingValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of increase in real estate investments related to improvements for entities with a substantial portion of business acquiring and holding investment real estate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 970 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Footnote 4)) -URI http://asc.fasb.org/extlink&oid=120402810&loc=d3e638233-123024 + Details
Name: | us-gaap_RealEstateImprovements
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of increase in real estate investments from acquisitions other than through foreclosure for entities with a substantial portion of business acquiring and holding investment real estate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 970 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Footnote 4)) -URI http://asc.fasb.org/extlink&oid=120402810&loc=d3e638233-123024 + Details
Name: | us-gaap_RealEstateOtherAcquisitions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | us-gaap_ReconciliationOfCarryingAmountOfRealEstateInvestmentsRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration