Pension and Employee Benefit Plans - Components of Pension and Employee Benefit Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 113	$ 112
Interest cost	329	356
Expected return on plan assets	(431)	(457)
Amortization of net actuarial loss	57	53
Net periodic benefit cost	68	64
Health Care Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1	1
Amortization of loss	2	3
Net periodic benefit cost	$ 3	$ 4