Employee Pension Benefits - Schedule of Changes in Components of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Compensation and Retirement Disclosure [Abstract]
Accumulated Other Comprehensive Income Before Tax - Beginning Balance			$ 1,854
Net actuarial loss - Before Tax			1
Amortization of Prior service costs (credits)- Before Tax			(1,166)
Accumulated Other Comprehensive Income Before Tax - Ending Balance	$ 689		689
Income Tax Benefit (Expense) - Beginning Balance			(653)
Net actuarial loss - Tax Effect			0
Amortization of Prior service costs (credits)- Tax Effect			451
Income Tax Benefit (Expense) - Ending Balance	(202)		(202)
Accumulated Other Comprehensive Income Net of Income Tax - Beginning Balance			1,201
Net actuarial loss - Net of Income Tax			1
Amortization of Prior service costs (credits)- Net of Income Tax	(238)	$ (238)	(715)	$ (714)
Accumulated Other Comprehensive Income Net of Income Tax - Ending Balance	$ 487		$ 487