Environmental Obligations - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended
	Jul. 31, 2012	Dec. 31, 2012	Dec. 31, 2011 Property	Dec. 31, 2010	Dec. 31, 2009
Environmental Matters And Other Commitments And Contingencies [Line Items]
Payment for pollution legal liability insurance policy	$ 3,062,000
Pollution legal liability insurance policy duration	10 years
Number of properties for which Marketing would not be able to meet its environmental remediation obligations			246
Accrued Marketing Environmental liabilities			47,874,000
Environmental costs, impairment charges			17,017,000
Asset retirement obligations removed from balance sheet		11,153,000
Deferred rental revenue		1,358,000
Environmental remediation obligations		46,150,000	57,700,000	10,908,000	12,645,000
Accretion expense		3,174,000	899,000	775,000
The amount of credits to Environmental Expenses		4,154,000
Increase in carrying value of property		5,710,000	47,874,000
Estimated remaining useful life of underground storage tank for capitalized asset retirement costs		10 years
Capitalized asset retirement costs		23,549,000	35,321,000
USTs [Member]
Environmental Matters And Other Commitments And Contingencies [Line Items]
Net asset cost related to USTs removed from the balance sheet		9,795,000
Capitalized Asset Retirement Cost [Member]
Environmental Matters And Other Commitments And Contingencies [Line Items]
Depreciation and amortization expense for capitalized asset retirement costs		5,371,000	855,000
Maximum [Member]
Environmental Matters And Other Commitments And Contingencies [Line Items]
Pollution legal liability insurance policy aggregate limit	$ 50,000,000