Additional payments to acquire commercial real estate.

No definition available.

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

- Definition

Number of property whose construction is completed.

+ References

No definition available.

+ Details

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Namespace Prefix:	gty_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of property whose construction is completed in current quarter.

+ References

No definition available.

+ Details

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Namespace Prefix:	gty_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479907/805-20-50-5

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Amortized cost, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481990/310-10-45-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-04(5)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479170/946-210-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-5

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

+ Details

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

- Definition

The number of real estate properties owned as of the statement of financial position to which the entity has fee simple title.

+ References

No definition available.

+ Details

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

- Definition

The cash outflow from the acquisition of property as primarily intended to generate income for its owner.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 13
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-13

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
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Period Type:

Property Acquisitions - Additional Information (Detail) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2024 USD ($) Property	Sep. 30, 2023 USD ($) Property	Dec. 31, 2023 USD ($) Property
Business Acquisition [Line Items]
Number of real estate properties, fee simple \| Property	52	37
Aggregate purchase price of properties acquired during the period	$ 204,488	$ 192,988
Number of property whose construction is completed \| Property	11
Number Of property whose construction is completed in current quarter \| Property	10
Finance receivables	$ 55,100
Ten Properties [Member]
Business Acquisition [Line Items]
Finance receivables	51,300
Accounting Standards Update 2016-13 [Member]
Business Acquisition [Line Items]
Aggregate purchase price of properties acquired during the period	$ 12,100
Express Tunnel Car Washes Under Construction [Member]
Business Acquisition [Line Items]
Number of real estate properties, fee simple \| Property	15	13	15
Aggregate purchase price of properties acquired during the period		$ 40,000	$ 45,800
Additional payments to acquire properties	$ 27,900	4,200
Express Tunnel Car Washes Under Construction [Member] \| Accounting Standards Update 2016-13 [Member]
Business Acquisition [Line Items]
Aggregate purchase price of properties acquired during the period	$ 73,700	$ 44,200