Pension and Employee Benefit Plans - Components of Pension and Employee Benefit Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 326	$ 298	$ 652	$ 595
Expected return on plan assets	(313)	(378)	(627)	(756)
Amortization of net actuarial loss	65	59	132	119
Net periodic benefit cost (gain)	78	(21)	157	(42)
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 cost (gain)	$ 3	$ 3	$ 5	$ 5