Employee Benefit Plans - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Defined benefit pension plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,166	$ 1,422
Interest cost	5,320	6,141
Expected return on plan assets	(5,733)	(6,473)
Amortization of prior service cost	8	8
Recognized actuarial loss	1,820	1,836
Net periodic benefit cost	2,581	2,934
Postretirement benefit plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	13
Interest cost	255	286
Recognized actuarial loss	37	37
Net periodic benefit cost	$ 293	$ 336