Pension and Employee Benefit Plans - Components of Pension and Employee Benefit Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 194	$ 258	$ 388	$ 516
Expected return on plan assets	(378)	(350)	(756)	(700)
Amortization of net actuarial loss	103	65	206	130
Net periodic benefit (gain) cost	(81)	(27)	(162)	(54)
Health Care Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1	1	1	1
Amortization of loss	2	2	4	4
Net periodic benefit (gain) cost	$ 3	$ 3	$ 5	$ 5