Property Acquisitions - Additional Information (Detail) (USD $)	12 Months Ended				1 Months Ended						1 Months Ended
	Dec. 31, 2012 Property	Dec. 31, 2010 Property	Jan. 31, 2011 CPD NY [Member]	Jan. 31, 2011 Land [Member] CPD NY [Member]	Jan. 31, 2011 CPD Lease [Member] Terms	Jan. 31, 2011 CPD Loan [Member]	Mar. 31, 2011 Nouria Lease [Member] Terms	Mar. 31, 2011 Nouria Loan [Member]	Jan. 31, 2011 ExxonMobil [Member] Property	Jan. 31, 2011 CPD NY Energy Corp. [Member] Property	Mar. 31, 2011 Nouria Energy Ventures [Member] Property	Mar. 31, 2011 Nouria [Member]	Mar. 31, 2011 Nouria [Member] Land [Member]
Business Acquisition [Line Items]
Number of gasoline stations acquired during year	5
Properties in separate transactions for an aggregate purchase price	$ 5,159,000
The number of Mobil-branded gasoline stations in which we took a security interest										59
Number of other Mobil-branded gasoline stations in which we took a security interest										6
Sale/leaseback transaction investment										111,621,000	87,047,000
Acquisition of real estate assets									65		66
Sale/leaseback, initial term in years					15 years		20 years
Sale/leaseback number of renewal terms					3		2
The number of years in the final renewal term for Nouria						10 years
Self amortizing loan term						10 years
Purchase price allocation, assets acquired				60,610,000									37,875,000
Leasehold interest as Lessee accounted as deferred asset			953,000									3,895,000
Leasehold interest as Lessor accounted as deferred liability			2,516,000									3,768,000
Purchase price allocated to direct financing and capital lease assets			38,752,000									37,315,000
Purchase price accounted for in notes, mortgages and accounts receivable, net			18,400,000									12,000,000
Capital lease obligation			5,768,000									1,114,000
Transaction cost related to acquisition			1,190,000									844,000
Extendable maturity period for each renewable term								Ten Years
Number of final renewal term							1
Number of years in final lease term renewal							5 years
Number of property purchase		3
Purchase price of property		$ 3,567,000