Schedule of Amounts Recognized in Accumulated Other Comprehensive Loss (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Pension and Other Postretirement Benefits Recognized in Accumulated Other Comprehensive Income (Loss) [Line Items]
Deferred taxes	$ (11,582)	$ (12,297)	$ (7,269)
Defined Benefit Pension Plans
Schedule of Pension and Other Postretirement Benefits Recognized in Accumulated Other Comprehensive Income (Loss) [Line Items]
Prior service cost	656	888
Total recognized in other comprehensive (income) loss before tax	656	888
Deferred taxes	321	236
Total recognized in other comprehensive income (loss), net of tax	977	1,124
Post-Retirement Benefit Plans
Schedule of Pension and Other Postretirement Benefits Recognized in Accumulated Other Comprehensive Income (Loss) [Line Items]
Prior service cost	(3,427)	(4,025)
Total recognized in other comprehensive (income) loss before tax	(3,427)	(4,025)
Deferred taxes	(445)	(227)
Total recognized in other comprehensive income (loss), net of tax	$ (3,872)	$ (4,252)