Amounts Recognized in Consolidated Balance Sheets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Current liabilities	$ (9,052)	$ (8,733)
Noncurrent liabilities	(248,615)	(209,859)
Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Current liabilities	(5,745)	(5,343)
Noncurrent liabilities	(236,055)	(195,982)
Net amount recognized	(241,800)	(201,325)
Post-retirement
Defined Benefit Plan Disclosure [Line Items]
Current liabilities	(3,307)	(3,390)
Noncurrent liabilities	(31,774)	(30,325)
Net amount recognized	$ (35,081)	$ (33,715)