Pension and Employee Benefit Plans - Components of Pension and Employee Benefit Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 112	$ 58
Interest cost	356	354
Expected return on plan assets	(457)	(502)
Amortization of net actuarial loss	53	65
Net periodic benefit cost (gain)	64	(25)
Health Care Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1	1
Amortization of loss	3	2
Net periodic benefit cost (gain)	$ 4	$ 3