Pension and Employee Benefit Plans - Components of Pension and Employee Benefit Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 112	$ 59	$ 223	$ 117
Interest cost	356	352	713	706
Expected return on plan assets	(457)	(503)	(914)	(1,005)
Amortization of net actuarial loss	53	64	106	129
Net periodic benefit cost (gain)	64	(28)	128	(53)
Health Care Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1	2	2	3
Amortization of loss	3	1	5	3
Net periodic benefit cost (gain)	$ 4	$ 3	$ 7	$ 6