Name:	gty_CapitalLeasesNetInvestmentInDirectFinancingLeasesIncreaseDecreaseInAllowancesReductionsForCreditLosses
Namespace Prefix:	gty_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

The total amount of revenue recognized for the period from operating leases, direct financing leases, above and below market leases and sublease revenue.

No definition available.

Name:	gty_IncomeStatementLeaseRevenue
Namespace Prefix:	gty_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Leases.

No definition available.

Name:	gty_LeasesLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The number of real estate properties in the portfolio, consisting of properties owned and properties leased from third party landlords.

No definition available.

Name:	gty_NumberOfPropertiesInPortfolio
Namespace Prefix:	gty_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The number of real estate properties leased from third-party landlords as of the balance sheet date.

No definition available.

Name:	gty_NumberOfPropertiesLeasedFromLandlords
Namespace Prefix:	gty_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The number of states in which the company's properties, comprised of those that are owned and those that are leased from third party landlords, are located.

No definition available.

Name:	gty_NumberOfStatesInWhichPropertiesAreLocated
Namespace Prefix:	gty_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Real estate non-cash adjustments.

No definition available.

Name:	gty_RealEstateNonCashAdjustments
Namespace Prefix:	gty_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The dollar amount of real estate taxes and other municipal charges paid by the company and then reimbursed by tenants included in revenues from rental properties and rental property expenses.

No definition available.

Name:	gty_RealEstateTaxesAndOtherMunicipalChargesPaidThenReimbursedByTenantsIncludedInRevenuesAndExpenses
Namespace Prefix:	gty_
Data Type:	xbrli:monetaryItemType
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The number of real estate properties owned as of the balance sheet date.

No definition available.

Name:	us-gaap_NumberOfRealEstateProperties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Amount of operating lease income from lease payments and variable lease payments paid and payable to lessor. Includes, but is not limited to, variable lease payments not included in measurement of lease receivable.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479773/842-30-50-5

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-6A

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479016/842-30-45-3

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Present value of lessee's discounted obligation for lease payments from operating lease.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479041/842-20-45-1

Name:	us-gaap_OperatingLeaseLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of lessee's right to use underlying asset under operating lease.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479041/842-20-45-1

Name:	us-gaap_OperatingLeaseRightOfUseAsset
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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Namespace Prefix:
Data Type:	na
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Name:	us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201613Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_CounterpartyNameAxis=gty_ThirdPartyLandlordsMember
Namespace Prefix:
Data Type:	na
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