Pension and Employee Benefit Plans - Components of Pension and Employee Benefit Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 97
Interest cost	$ 326	298
Expected return on plan assets	(313)	(476)
Amortization of net actuarial loss	65	59
Net periodic benefit cost (gain)	78	(22)
Health Care Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1	1
Amortization of loss	2	2
Net periodic benefit cost (gain)	$ 3	$ 3