Employee Pension Benefits - Components of Net Periodic Pension Benefit of Pension Plan and Excess Pension Plan (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Interest cost	$ 403	$ 409
Expected return on assets	(1,225)	(1,383)
Recognized net actuarial loss	0	1
Amortization of prior service (credit)	(388)	(389)
Net periodic pension (benefit)	$ (1,210)	$ (1,362)