Schedule III - Real Estate and Accumulated Depreciation and Amortization Part 18 (Parenthetical) (Detail)	12 Months Ended
Dec. 31, 2023
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation Disclosure [Abstract]
Date of Initial Leasehold or Acquisition Investment	vaious

The period description for the initial cost of leasehold or acquisition investment to Company.

No definition available.

Name:	gty_InitialCostOfLeaseholdOrAcquisitionInvestmentToCompanyPeriodDescription
Namespace Prefix:	gty_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration