Pension and Employee Benefit Plans - Components of Pension and Employee Benefit Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 194	$ 258
Expected return on plan assets	(378)	(350)
Amortization of net actuarial loss	103	65
Net periodic benefit (gain) cost	(81)	(27)
Health Care Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1	1
Amortization of loss	2	2
Net periodic benefit (gain) cost	$ 3	$ 3