Pensions and Other Post-retirement Benefits - Components of Net Periodic Benefit Cost (Credit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 10,342	$ 11,125	$ 11,023
Interest cost	18,803	17,214	18,450
Expected return on plan assets	(38,644)	(36,352)	(35,417)
Amortization of transition amounts	2	1	2
Amortization of prior service cost (credit)	223	(21)	(19)
Recognized net actuarial losses	10,159	13,755	12,955
Settlement/curtailment loss (credit)	2,497	179	148
Special termination charge	0	0	11,384
Net periodic benefit cost(a)	3,382	5,901	18,526
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	354	369	403
Interest cost	996	793	882
Expected return on plan assets	0	0	0
Amortization of transition amounts	0	0	0
Amortization of prior service cost (credit)	(405)	(405)	(307)
Recognized net actuarial losses	869	752	100
Settlement/curtailment loss (credit)	0	0	(562)
Special termination charge	0	0	0
Net periodic benefit cost(a)	$ 1,814	$ 1,509	$ 516