Employee Pension Benefits - Schedule of Changes in Components of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2015	Mar. 31, 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	(389)
Accumulated Other Comprehensive Income Before Tax - Ending Balance	1,466
Income Tax Benefit (Expense) - Beginning Balance	(653)
Net actuarial loss - Tax Effect	0
Amortization of Prior service costs (credits)- Tax Effect	150
Income Tax Benefit (Expense) - Ending Balance	(503)
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	(239)	$ (238)
Accumulated Other Comprehensive Income Net of Income Tax - Ending Balance	$ 963