Employee Pension Benefits - Schedule of Changes in Components of Accumulated Other Comprehensive Loss (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Compensation And Retirement Disclosure [Abstract]
Accumulated Other Comprehensive Income (Loss) Before Tax - Beginning Balance			$ (13,058)
Amortization of Actuarial (gains)/losses - Before Tax			1,518
Amortization of Prior service costs (credits)- Before Tax			(1,167)
Accumulated Other Comprehensive Income (Loss) Before Tax - Ending Balance	(12,707)		(12,707)
Income Tax Benefit (Expense) - Beginning Balance			5,128
Amortization of Actuarial (gains)/losses - Tax Effect	(196)	(265)	(589)	(796)
Amortization of Prior service costs (credits)- Tax Effect			453
Income Tax Benefit (Expense) - Ending Balance	4,992		4,992
Accumulated Other Comprehensive Income (Loss) Net of Income Tax - Beginning Balance			(7,930)
Amortization of Actuarial (gains)/losses - Net of Income Tax	310	414	929	1,241
Amortization of Prior service costs (credits)- Net of Income Tax	(238)	(237)	(714)	(711)
Accumulated Other Comprehensive Income (Loss) Net of Income Tax - Ending Balance	$ (7,715)		$ (7,715)