Employee Pension Benefits - Schedule of Changes in Components of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 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			(778)
Accumulated Other Comprehensive Income Before Tax - Ending Balance	$ 1,077		1,077
Income Tax Benefit (Expense) - Beginning Balance			(653)
Net actuarial loss - Tax Effect			0
Amortization of Prior service costs (credits)- Tax Effect			301
Income Tax Benefit (Expense) - Ending Balance	(352)		(352)
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)	(477)	$ (476)
Accumulated Other Comprehensive Income Net of Income Tax - Ending Balance	$ 725		$ 725