Commitments and Contingencies - Changes in Accrued Environmental Remediation and Related Costs (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Commitments And Contingent Liabilities [Line Items]
Balance at the beginning of the period	$ 48,006
Additions charged to expense, net	12,749
Payments, net	(2,742)
Balance at the end of the period	58,013
Amounts recognized in the Condensed Consolidated Balance Sheet at the end of the period:
Current liability	4,657	5,667
Noncurrent liability	53,356	42,339
Total	$ 58,013