Employee Benefit Plans - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Defined benefit pension plans
Defined Benefit Plan Disclosure [Line Items]
Service cost (credit)	$ 1,609	$ 624	$ 4,293	$ 4,988
Interest cost	6,107	7,036	18,407	19,568
Expected return on plan assets	(6,393)	(7,356)	(19,309)	(22,629)
Amortization of prior service cost (credit)	8	6	23	(522)
Recognized actuarial loss	1,732	3,138	5,194	12,919
Curtailment gain	0	0	0	(8,639)
Settlement loss	1,495	5,233	1,495	5,233
Net periodic benefit cost	4,558	8,681	10,103	10,918
Postretirement benefit plans
Defined Benefit Plan Disclosure [Line Items]
Service cost (credit)	13	(1)	39	41
Interest cost	286	270	857	896
Recognized actuarial loss	37	34	111	111
Net periodic benefit cost	$ 336	$ 303	$ 1,007	$ 1,048