Benefit Plans - Net Periodic Benefit Cost (Increase) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 0	$ 0
Interest cost	1,198	1,094	1,227
Return on plan assets	(2,562)	(2,769)	(2,550)
Amortization of net loss (gain)	1,015	795	920
Amortization of unrecognized prior service cost	0	0	0
Net periodic benefit (increase) cost	(349)	(880)	(403)
Post-retirement
Defined Benefit Plan Disclosure [Line Items]
Service cost	80	115	105
Interest cost	837	786	871
Return on plan assets	0	0	0
Amortization of net loss (gain)	(825)	(396)	(677)
Amortization of unrecognized prior service cost	0	0	0
Net periodic benefit (increase) cost	$ 92	$ 505	$ 299