Leases - Additional Information (Detail) (USD $)	1 Months Ended			3 Months Ended		12 Months Ended
	Dec. 31, 2012 Portfolios State Property	Sep. 30, 2012	May 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2012 Property Portfolios State	Dec. 31, 2011	Dec. 31, 2010
Leases [Line Items]
Number of properties leased for other retail purposes	20					20
Number of properties marketed for sale and which have temporary occupancies						40
Number of properties	1,081					1,081
Number of states in which our properties are located	21					21
Number of properties previously leased to GPMI	700					700
Number of new triple net leases we've entered into						10
Number of leased properties with new tenants						443
License agreements with occupants properties including Marketing's former sub-tenants						155
Properties which have had their underground storage tanks removed						40
Properties previously subject to the Master Lease that are vacant and marked for sale						60
Number of petroleum distributor property portfolios
Number of petroleum lease properties						443
Maximum lease commitment for capital expenditure						$ 14,080,000
Amount of asset retirement obligations removed from the balance sheet						11,153,000
Deferred rental revenue	1,358,000					1,358,000
Lease origination costs						3,146,000
Revenues from rental properties included in continuing operations						99,286,000	100,263,000	78,227,000
Revenues due or received from Marketing under the Master Lease						20,136,000	52,646,000	50,135,000
Revenues related to properties repositioned	45,515,000	26,426,000	72,954,000
Real estate taxes paid that were reimbursed by tenant						11,263,000	6,639,000	1,849,000
Revenues realized under interim fuel supply agreements						1,763,000
Increase rental revenue						4,433,000	2,102,000	1,666,000
Gross deferred receivable attributable to the Master Lease with Marketing that was fully reserved				25,630,000			25,630,000
Non-cash allowances for deferred rental revenue				11,043,000	8,715,000
Investment in direct financing lease	91,904,000					91,904,000
Investments in direct financing lease, minimum lease payments receivable	203,869,000					203,869,000
Investment in direct financing lease, unguaranteed estimated residual value	11,991,000					11,991,000
Investment in direct financing lease, deferred income	123,956,000					123,956,000
Rent expense on operating lease						7,903,000	8,009,000	7,007,000
Rent received under sublease						11,809,000	13,325,000	11,868,000
Remaining lease term						10 years
2013	7,826,000					7,826,000
2014	6,830,000					6,830,000
2015	5,631,000					5,631,000
2016	4,474,000					4,474,000
2017	2,771,000					2,771,000
Thereafter	5,866,000					5,866,000
USTs [Member]
Leases [Line Items]
Net asset costs related to USTs removed from the balance Sheet	9,795,000					9,795,000
Allowance for Doubtful Accounts [Member]
Leases [Line Items]
Bad debt reserve				8,802,000		13,980,000
Reduction to our bad debt reserves for Marketing						22,782,000
Deductions						1,348,000
Marketing Leases [Member]
Leases [Line Items]
Real estate taxes paid related to the portfolio previously leased to Marketing						$ 11,263,000	$ 6,639,000	$ 1,849,000
Minimum [Member]
Leases [Line Items]
Unitary triple-net lease agreements initial terms						15 years
Maximum [Member]
Leases [Line Items]
Unitary triple-net lease agreements successive terms						20 years