Pension and Post-Retirement Benefit Plans - Schedule of Components of Net Periodic Pension Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan settlement loss		$ 11,744		$ 11,744
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefit earned during the period	$ 321	317	$ 642	634
Interest cost on projected benefit obligation	1,862	2,173	3,724	4,516
Expected return on plan assets	(2,272)	(2,547)	(4,544)	(5,265)
Amortization of prior service cost	72	74	144	148
Amortization of actuarial loss	1,062	1,321	2,124	2,740
Defined benefit plan settlement loss		11,744		11,744
Net periodic pension cost	$ 1,045	$ 13,082	$ 2,090	$ 14,517