Pension and Employee Benefit Plans - Components of Pension and Employee Benefit Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 259	$ 326	$ 775	$ 977
Expected return on plan assets	(443)	(313)	(1,151)	(940)
Amortization of net actuarial loss	67	65	199	198
Net periodic benefit (gain) cost	(117)	78	(177)	235
Health Care Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1	1	2	2
Amortization of loss	2	2	6	6
Net periodic benefit (gain) cost	$ 3	$ 3	$ 8	$ 8