XML 45 R30.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Organization, Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) | 12 Months Ended
--- | ---
Dec. 31, 2017 USD ($) subsidiary shares | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Organization And Significant Accounting Policies [Line Items] |  |  |
Number of subsidiaries interest owned in general and limited partnership | subsidiary | 2 |  |
Non-qualifying income related to real estate portfolio | $ 0 |  |
Amortization related to below-market lease | 1,500,000 | $ 1,200,000 | $ 900,000
Total amortization expense related to intangible assets | $ 15,900,000 | 13,400,000 | 13,100,000
Maturity period of highly-liquid investments at the time of purchase | three months or less |  |
Payments of deferred financing costs | $ 1,990,000 | 1,500,000 | 1,880,000
Total amortization expense related to deferred financing costs is included in interest expense | $ 1,713,000 | 1,932,000 | 1,955,000
Uncertain tax positions percentage | 50.00% |  |
Uncertain tax positions | $ 0 | 0 | 0
Accrued liabilities | 0 | 0 | 100,000
Expenses recorded to general and administrative expense | 100,000 | 100,000 | 200,000
Aggregate undiscounted obligation on properties | 6,300,000 |  |
Above Market Leases |  |  |
Organization And Significant Accounting Policies [Line Items] |  |  |
Amortization related to above-market lease | $ 700,000 | $ 500,000 | $ 400,000
Minimum |  |  |
Organization And Significant Accounting Policies [Line Items] |  |  |
Expected lease up period for estimating carrying costs | 9 months |  |
Remaining term of in-place leases and unamortized lease | 7 years |  |
REIT taxable income to its stockholders (as percent) | 90.00% |  |
Percentage of discount rate for calculating undiscounted obligation (as percent) | 2.50% |  |
Maximum |  |  |
Organization And Significant Accounting Policies [Line Items] |  |  |
Expected lease up period for estimating carrying costs | 18 months |  |
Remaining term of in-place leases and unamortized lease | 15 years |  |
REIT taxable income to its stockholders (as percent) | 100.00% |  |
Percentage of discount rate for calculating undiscounted obligation (as percent) | 7.00% |  |
Building and Improvements |  |  |
Organization And Significant Accounting Policies [Line Items] |  |  |
Estimated useful life | 39 years |  |
Equipment and Fixtures | Minimum |  |  |
Organization And Significant Accounting Policies [Line Items] |  |  |
Estimated useful life | 5 years |  |
Equipment and Fixtures | Maximum |  |  |
Organization And Significant Accounting Policies [Line Items] |  |  |
Estimated useful life | 20 years |  |
GCLP Business Trust I |  |  |
Organization And Significant Accounting Policies [Line Items] |  |  |
Subsidiary and business trust of the Company, formed under the laws of the Commonwealth of Massachusetts, date | Dec. 28, 2005 |  |
Percentage of limited partnership interest transferred to business unit (as percent) | 99.00% |  |
Number of trust shares exchanged for limited partnership interest (in shares) | shares | 100 |  |
Gladstone Commercial Advisers, Inc. |  |  |
Organization And Significant Accounting Policies [Line Items] |  |  |
Company ownership percentage of voting securities of Commercial Advisers (as percent) | 100.00% |  |
GCLP Business Trust II |  |  |
Organization And Significant Accounting Policies [Line Items] |  |  |
Subsidiary and business trust of the Company, formed under the laws of the Commonwealth of Massachusetts, date | Dec. 28, 2005 |  |
Percentage of limited partnership interest transferred to business unit (as percent) | 1.00% |  |
Number of trust shares exchanged for general partnership interest (in shares) | shares | 100 |  |

X
- Definition Date when an entity was incorporated + References No definition available. + Details
Name: | dei_EntityIncorporationDateOfIncorporation
Namespace Prefix: | dei_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

X
- Definition Aggregate undiscounted obligation on properties. + References No definition available. + Details
Name: | good_AggregateUndiscountedObligationOnProperties
Namespace Prefix: | good_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Cash equivalents maximum maturity period of highly liquid investments. + References No definition available. + Details
Name: | good_CashEquivalentsMaximumMaturityPeriodOfHighlyLiquidInvestments
Namespace Prefix: | good_
Data Type: | us-types:durationStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Expected lease up period. + References No definition available. + Details
Name: | good_ExpectedLeaseUpPeriod
Namespace Prefix: | good_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Minimum percentage likelihood to recognize tax benefit from uncertain tax position. + References No definition available. + Details
Name: | good_MinimumPercentageLikelihoodToRecognizeTaxBenefitFromUncertainTaxPosition
Namespace Prefix: | good_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Non qualifying income related to real estate portfolio. + References No definition available. + Details
Name: | good_NonQualifyingIncomeRelatedToRealEstatePortfolio
Namespace Prefix: | good_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Number of subsidiaries interest owned in general and limited partnership. + References No definition available. + Details
Name: | good_NumberOfSubsidiariesInterestOwnedInGeneralAndLimitedPartnership
Namespace Prefix: | good_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of trust shares exchanged for general partnership interest. + References No definition available. + Details
Name: | good_NumberOfTrustSharesExchangedForGeneralPartnershipInterest
Namespace Prefix: | good_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of trust shares exchanged for limited partnership interest. + References No definition available. + Details
Name: | good_NumberOfTrustSharesExchangedForLimitedPartnershipInterest
Namespace Prefix: | good_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Organization and significant accounting policies. + References No definition available. + Details
Name: | good_OrganizationAndSignificantAccountingPoliciesLineItems
Namespace Prefix: | good_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of annual real estate investment trust taxable income distribute to stockholders. + References No definition available. + Details
Name: | good_PercentageOfAnnualRealEstateInvestmentTrustTaxableIncomeDistributeToStockholders
Namespace Prefix: | good_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of discount rate for calculating undiscounted obligation. + References No definition available. + Details
Name: | good_PercentageOfDiscountRateForCalculatingUndiscountedObligation
Namespace Prefix: | good_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of limited partnership interest transferred to business unit. + References No definition available. + Details
Name: | good_PercentageOfLimitedPartnershipInterestTransferredToBusinessUnit
Namespace Prefix: | good_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Remaining term of in place leases and unamortized lease. + References No definition available. + Details
Name: | good_RemainingTermOfInPlaceLeasesAndUnamortizedLease
Namespace Prefix: | good_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of amortization of acquired leases acquired as part of a real property acquisition at below market lease rate with a finite life. + References No definition available. + Details
Name: | us-gaap_AmortizationOfBelowMarketLease
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of amortization expense attributable to debt issuance costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(8)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(8)) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_AmortizationOfFinancingCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
Name: | us-gaap_AmortizationOfIntangibleAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The expense charged against earnings for the periodic recognition of capitalized leases. This element may apply to energy companies that lease mineral producing properties and to other enterprises that capitalize property, plant, or equipment obtained through capital leases. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84164758&loc=d3e45031-112735 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585 + Details
Name: | us-gaap_AmortizationOfLeasedAsset
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6392676&loc=d3e7480-110848 + Details
Name: | us-gaap_AssetRetirementObligationAccretionExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of increase (decrease) in asset retirement obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
Name: | us-gaap_AssetRetirementObligationPeriodIncreaseDecrease
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- Definition The parent entity's interest in net assets of the subsidiary, expressed as a percentage. + References No definition available. + Details
Name: | us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The cash outflow for loan and debt issuance costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585 + Details
Name: | us-gaap_PaymentsOfFinancingCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of unrecognized tax benefits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319 + Details
Name: | us-gaap_UnrecognizedTaxBenefits
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_AboveMarketLeasesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingAndBuildingImprovementsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=good_EquipmentAndFixturesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConsolidatedEntitiesAxis=us-gaap_SubsidiariesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=good_SubsidiariesTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=good_SubsidiariesOneMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |