Employee Pension Benefits - Schedule of Changes in Components of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Accumulated Other Comprehensive Income (Loss) Before Tax - Beginning Balance	$ (2,869)
Actuarial (gains) losses	0
Prior service costs (credits)	(388)
Accumulated Other Comprehensive Income (Loss) Before Tax - Ending Balance	(3,257)
Income Tax Benefit (Expense) - Beginning Balance	1,176
Actuarial (gains) losses	0	$ 0
Prior service costs (credits)	149
Income Tax Benefit (Expense) - Ending Balance	1,325
Accumulated Other Comprehensive Income (Loss) Net of Income Tax - Beginning Balance	(1,693)
Actuarial (gains) losses	0	1
Prior service costs (credits)	(239)	$ (239)
Accumulated Other Comprehensive Income (Loss) Net of Income Tax - Ending Balance	$ (1,932)