Property Acquisitions - Additional Information (Detail)	1 Months Ended		6 Months Ended
	May 31, 2021 USD ($) Center Option	Feb. 29, 2020 USD ($) Property Option	Jun. 30, 2021 USD ($) Property Option	Jun. 30, 2020 USD ($) Property
Business Acquisition [Line Items]
Number of real estate properties, fee simple | Property			55
Aggregate purchase price of properties acquired during the period			$ 63,304,000	$ 68,671,000
Number of car wash properties acquired during the period | Property				15
Properties Acquired in Separate Transactions [Member]
Business Acquisition [Line Items]
Aggregate purchase price of properties acquired during the period			7,905,000	$ 18,368,000
Purchase price allocated to land			1,865,000	7,886,000
Purchase price allocated to buildings and improvements			5,396,000	9,508,000
Purchase price allocated to in-place leases			$ 644,000	$ 974,000
Number of car wash properties acquired during the period | Property			2
Number of convenience store, gasoline station and other automotive related properties acquired during the period | Property				5
Properties Acquired on May 2021 [Member]
Business Acquisition [Line Items]
Aggregate purchase price of properties acquired during the period	$ 31,018,000
Number of oil change centers acquired during the period | Center	46
Initial term of lease	11 years 6 months
Number of lease renewal options | Option	3
Lease, renewal term	5 years
Lease description			The leases require our tenant 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 every five years during the initial and renewal terms of the lease.
Intervals of rent increase	5 years
Purchase price allocated to land	$ 4,551,000
Purchase price allocated to buildings and improvements	22,539,000
Purchase price allocated to in-place leases	3,120,000
Purchase price allocated to above market leases	2,224,000
Purchase price allocated to below market leases	$ 1,416,000
Properties Acquired on March, April, May 2021 [Member]
Business Acquisition [Line Items]
Aggregate purchase price of properties acquired during the period			$ 24,381,000
Purchase price allocated to land			4,081,000
Purchase price allocated to buildings and improvements			18,262,000
Purchase price allocated to in-place leases			$ 2,038,000
Number of car wash properties acquired during the period | Property			7
Unitary lease description			The unitary lease requires our tenant 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			5
Unitary lease renewal term			5 years
Properties Acquired on February 2020 [Member]
Business Acquisition [Line Items]
Aggregate purchase price of properties acquired during the period		$ 50,303,000
Purchase price allocated to land		4,775,000
Purchase price allocated to buildings and improvements		41,093,000
Purchase price allocated to in-place leases		3,727,000
Purchase price allocated to above market leases		1,955,000,000
Purchase price allocated to below market leases		$ 1,247,000,000
Number of car wash properties acquired during the period | Property		10
Unitary lease description			The unitary lease requires our tenant 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		5
Unitary lease renewal term		5 years