Pension and Other Post-Retirement Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits
Components of net periodic pension expense (credit):
Interest cost	$ 5,660	$ 5,085	$ 5,616
Amortization of past-service liability	0
Expected return on plan assets	(13,933)	(16,139)	(16,290)
Amortization of net actuarial loss	10,035	7,179	8,209
Net periodic pension expense (credit)	1,762	(3,875)	(2,465)
Post- Retirement Benefits
Components of net periodic pension expense (credit):
Service cost	0
Interest cost	512	513	577
Amortization of past-service liability	(249)	(249)	(249)
Amortization of net actuarial loss	124	309	274
Net periodic pension expense (credit)	$ 387	$ 573	$ 602