Environmental Obligations - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Jul. 31, 2012	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
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 for environmental contamination discovered (other than as a result of a voluntary site investigation) during the first 10 years of the lease term (or a shorter period for a minority of such leases).
Environmental remediation obligations		$ 63,565,000	$ 74,516,000
Accretion expense		3,448,000	4,107,000	$ 4,829,000
Amounts of credits to environmental expenses included in continuing and discontinued operations		6,854,000	7,007,000	4,639,000
Increase in carrying value of property		5,477,000	11,346,000
Non-cash impairment charges		$ 6,932,000	11,658,000
Estimated remaining useful life of underground storage tank for capitalized asset retirement costs		10 years
Depreciation and amortization expense for capitalized asset retirement costs		$ 4,347,000	5,126,000	$ 5,997,000
Capitalized asset retirement costs		45,380,000	49,125,000
Reasonably Estimable Environmental Remediation Obligation [Member]
Other Commitments [Line Items]
Environmental remediation obligations		18,537,000	29,507,000
Future Environmental Liabilities for Preexisting Unknown Contamination [Member]
Other Commitments [Line Items]
Environmental remediation obligations		45,028,000	45,009,000
Capitalized asset retirement costs		26,688,000	28,489,000
Known Environmental Liabilities [Member]
Other Commitments [Line Items]
Capitalized asset retirement costs		$ 18,692,000	$ 20,636,000
Minimum [Member]
Other Commitments [Line Items]
Environmental remediation liabilities discount range		4.00%
Environmental remediation liabilities fair value, expected future net cash flows		2.00%
Maximum [Member]
Other Commitments [Line Items]
Environmental remediation liabilities discount range		7.00%
Environmental remediation liabilities fair value, expected future net cash flows		2.75%