Commitments and Contingencies - Changes in Accrued Environmental Remediation and Related Costs (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Commitments And Contingencies Disclosure [Abstract]
Balance at the beginning of the period	$ 48,006
Additions charged to expense, net	13,041
Payments, net	(1,256)
Balance at the end of the period	59,791
Amounts recognized in the Condensed Consolidated Balance Sheet at the end of the period:
Current liability	4,754	5,667
Noncurrent liability	55,037	42,339
Total	$ 59,791