Employee Benefit Plans - Components of Net Periodic Benefit Cost (Gain) (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Pension Plan, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Interest cost	$ 101	$ 99
Expected return on plan assets	(142)	(148)
Settlement loss	21
Recognized net actuarial loss	58	57
Net periodic cost	38	8
Other Postretirement Benefit Plan, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	17	17
Interest cost	21	23
Net periodic cost	$ 38	$ 40