Retirement Plans and Other Postretirement Benefits - Components of Net Periodic Benefit Cost (Income) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 436	$ 560	$ 524
Interest cost	1,905	1,760	1,927
Expected loss on plan assets	(3,061)	(3,287)	(3,074)
Amortization of net actuarial loss	1,176	1,120	1,185
Accretion of prior service cost	(181)	(283)	(282)
Net periodic benefit cost (income)	275	(130)	280
Other Post Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	67	88	48
Interest cost	94	92	118
Expected loss on plan assets	0	0	0
Amortization of net actuarial loss	0	4	42
Accretion of prior service cost	0	0	0
Net periodic benefit cost (income)	$ 161	$ 184	$ 208