Pension and Employee Benefit Plans - Components of Pension and Employee Benefit Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 58	$ 50	$ 175	$ 150
Interest cost	354	357	1,060	1,071
Expected return on plan assets	(502)	(488)	(1,507)	(1,464)
Amortization of net actuarial loss	65	44	194	132
Net periodic benefit cost (gain)	(25)	(37)	(78)	(111)
Health Care Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1	1	4	3
Amortization of loss (gain)	2	$ (1)	5	$ (3)
Net periodic benefit cost (gain)	$ 3		$ 9