Employee Benefit Plans - Components of Net Periodic Benefit Cost (Gain) (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Pension Plan, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Interest cost	$ 99	$ 106
Expected return on plan assets	(148)	(151)
Amortization of unrecognized net loss		28
Recognized net actuarial loss	57
Net periodic (benefit) cost	8	(17)
Other Postretirement Benefit Plan, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	17	12
Interest cost	23	22
Net periodic (benefit) cost	$ 40	$ 34