Property Acquisitions - Additional Information (Detail)					12 Months Ended
	Aug. 01, 2018 USD ($) Property Option	Apr. 17, 2018 USD ($) Property Option	Oct. 03, 2017 USD ($) Property Option Restaurant	Sep. 06, 2017 USD ($) Property Option	Dec. 31, 2018 USD ($) Property	Dec. 31, 2017 USD ($) Property	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Number of gasoline stations and convenience stores acquired during the period | Property					41	103
Aggregate purchase price of the gasoline stations and convenience stores acquired during the period					$ 77,972,000	$ 214,000,000	$ 7,688,000
Number of stand-alone Burger King quick service restaurants acquired during the period | Restaurant			5
GPM Investments, LLC [Member]
Business Acquisition [Line Items]
Number of gasoline stations and convenience stores acquired during the period | Property		30			5
Aggregate purchase price of the gasoline stations and convenience stores acquired during the period		$ 52,592,000			$ 7,968,000
Unitary lease description					The unitary lease requires GPM to pay a fixed annual rent plus all amounts pertaining to the properties, including environmental expenses, real estate taxes, assessments, license and permit fees, charges for public utilities and all other governmental charges. Rent is scheduled to increase annually during the initial and renewal terms of the lease.
Unitary lease initial term		15 years
Number of unitary lease renewal options | Option		4
Unitary lease renewal term		5 years
Purchase price allocation, land acquired		$ 31,633,000			$ 4,929,000
Purchase price allocation, buildings and improvements acquired		17,489,000			2,753,000
Purchase price allocated to in-place leases		4,047,000			$ 286,000
Purchase price allocated to below market leases		$ 577,000
Applegreen PLC [Member]
Business Acquisition [Line Items]
Number of gasoline stations and convenience stores acquired during the period | Property	6
Aggregate purchase price of the gasoline stations and convenience stores acquired during the period	$ 17,412,000		$ 68,710,000
Unitary lease description					. The unitary lease requires Applegreen to pay a fixed annual rent plus all amounts pertaining to the properties, including environmental expenses, real estate taxes, assessments, license and permit fees, charges for public utilities and all other governmental charges. Rent is scheduled to increase annually during the initial and renewal terms of the lease.
Unitary lease initial term	15 years		15 years
Number of unitary lease renewal options | Option	4		4
Unitary lease renewal term	5 years		5 years
Purchase price allocation, land acquired	$ 8,930,000		$ 36,874,000
Purchase price allocation, buildings and improvements acquired	6,773,000		27,431,000
Purchase price allocated to in-place leases	1,371,000		4,548,000
Purchase price allocated to below market leases	435,000		1,104,000
Purchase price allocated to above market leases	$ 773,000		$ 961,000
Number of convenience stores and gasoline stations | Property			33
Empire Petroleum Partners, LLC [Member]
Business Acquisition [Line Items]
Number of gasoline stations and convenience stores acquired during the period | Property				49
Aggregate purchase price of the gasoline stations and convenience stores acquired during the period				$ 123,126,000
Unitary lease description					The unitary lease provides for an initial term of 15 years, with four five-year renewal options. The unitary lease requires Empire to pay a fixed annual rent plus all amounts pertaining to the properties including environmental expenses, real estate taxes, assessments, license and permit fees, charges for public utilities and all other governmental charges. Rent is scheduled to increase annually during the initial and renewal terms of the lease.
Unitary lease initial term				15 years
Number of unitary lease renewal options | Option				4
Unitary lease renewal term				5 years
Purchase price allocation, land acquired				$ 75,674,000
Purchase price allocation, buildings and improvements acquired				38,205,000
Purchase price allocated to in-place leases				9,058,000
Purchase price allocated to above market leases				$ 189,000
Gasoline Stations And Convenience Store Properties
Business Acquisition [Line Items]
Purchase price allocation, land acquired						5,800,000
Purchase price allocation, buildings and improvements acquired						14,424,000
Purchase price allocated to in-place leases						2,969,000
Purchase price allocated to below market leases						$ 1,028,000
Additional number of gasoline stations and convenience stores acquired during the period | Property						16
Additional aggregate purchase price of the gasoline stations and convenience stores acquired during the period						$ 22,164,000