Schedule of Amounts Recognized in Balance Sheets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Pension and Other Postretirement Benefits Disclosure [Line Items]
Accrued liabilities	$ (2,588)	$ (2,779)
Postretirement benefits other than pensions	(4,046)	(14,462)
Other liabilities	(95,430)	(82,199)
Total pension and other postretirement accrued benefit liability	$ (102,064)	$ (99,440)