Employee Benefit Plans - Components of Net Periodic Benefit Cost (Gain) (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Pension Plan, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Interest cost	$ 66	$ 71
Expected return on plan assets	(99)	(101)
Amortization of unrecognized net loss		19
Recognized net actuarial loss	37
Net periodic (benefit) cost	4	(11)
Other Postretirement Benefit Plan, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	11	8
Interest cost	15	15
Net periodic (benefit) cost	$ 26	$ 23