Leases - Marketing and the Master Lease - Additional Information (Detail)				9 Months Ended
	Nov. 03, 2015 USD ($)	Apr. 22, 2015 USD ($)	Mar. 03, 2015 USD ($)	Sep. 30, 2016 USD ($) Property Portfolios
Leases [Line Items]
Legal settlements received	$ 10,800,000
Number of new triple net leases entered into during the period | Portfolios				15
Number of leased properties with new tenants | Property				351
Number of leased properties as single unit triple net leases | Portfolios				20
Maximum lease commitment for capital expenditure				$ 10,805,000
Asset retirement obligations removed from balance sheet				13,769,000
Deferred rental revenue				2,961,000
USTs [Member]
Leases [Line Items]
Asset retirement obligations removed from balance sheet				13,769,000
Net asset retirement cost related to USTs removed from the balance sheet				10,808,000
Deferred rental revenue				$ 2,961,000
Minimum [Member]
Leases [Line Items]
Unitary triple-net lease agreements initial terms				15 years
Maximum [Member]
Leases [Line Items]
Unitary triple-net lease agreements initial terms				20 years
Unitary triple-net lease agreements successive terms				20 years
Getty Petroleum Marketing Inc [Member]
Leases [Line Items]
Number of properties previously leased | Property				397
Marketing Estate Liquidating Trustee [Member]
Leases [Line Items]
Settlement agreement date				Mar. 03, 2015
Settlement agreement hearing date				Apr. 22, 2015
Interim distribution amount			$ 6,800,000
Marketing Estate Liquidating Trustee [Member] | Settlement Agreement [Member]
Leases [Line Items]
Additional distribution amount		$ 550,000