Commitments and Contingencies - Changes in Accrued Environmental Remediation and Related Costs (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Commitments And Contingent Liabilities [Line Items]
Balance at the beginning of the period	$ 113,636
Additions charged to expense, net	5,769
Payments, net	(1,174)
Balance at the end of the period	118,231
Amounts recognized in the Condensed Consolidated Balance Sheet at the end of the period:
Current liability	12,457	4,859
Noncurrent liability	105,774	108,777
Total	$ 118,231