Environmental Obligations - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended
	Jul. 31, 2012	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Other Commitments [Line Items]
Pollution legal liability insurance policy duration	10 years
Pollution legal liability insurance policy aggregate limit	$ 50,000,000
Remediation agreement of lease		We have agreed to be responsible for environmental contamination at the premises that was known at the time the lease commenced, and that existed prior to commencement of the lease and is discovered (other than as a result of a voluntary site investigation) during the first ten years of the lease term.
Environmental remediation liability		94,945,000		91,566,000
Accretion expense		1,169,000	620,000
The amounts of credits to environmental expenses included in continuing operations and to earnings from operating activities in discontinued operations		49,000	359,000
Increase in carrying value of property		5,279,000	2,598,000
Non-cash impairment charges		4,805,000	1,242,000
Estimated remaining useful life of underground storage tank for capitalized asset retirement costs		10 years
Depreciation and amortization expense for capitalized asset retirement costs		1,636,000	335,000
Capitalized asset retirement costs		59,357,000		59,809,000
Asset retirement obligations removed from balance sheet		12,954,000
Deferred rental revenue		2,416,000
Minimum [Member]
Other Commitments [Line Items]
Environmental remediation liability discount range		4.00%
Environmental remediation liability fair value, expected future net cash flows		2.00%
Maximum [Member]
Other Commitments [Line Items]
Environmental remediation liability discount range		7.00%
Environmental remediation liability fair value, expected future net cash flows		2.75%
USTs [Member]
Other Commitments [Line Items]
Asset retirement obligations removed from balance sheet		12,954,000
Net asset cost related to USTs removed from the balance sheet		10,538,000
Deferred rental revenue		2,416,000
Future Environmental Liabilities [Member]
Other Commitments [Line Items]
Environmental remediation liability		47,999,000		49,700,000
Reasonably Estimable Environmental Remediation Obligation [Member]
Other Commitments [Line Items]
Environmental remediation liability		$ 46,946,000		$ 41,866,000