Commitments and Contingencies - Changes in Accrued Environmental Remediation and Related Costs (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Balance at the beginning of the period	$ 41,637
Additions charged to expense, net	14,098
Payments, net	(6,278)
Balance at the end of the period	49,457
Amounts recognized in the Condensed Consolidated Balance Sheet at the end of the period:
Current liability	6,580	7,301
Noncurrent liability	42,877	34,336
Total	$ 49,457