Employee Benefit Plans - Change in Benefit Obligation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Pension Plan, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit obligation, beginning of year	$ 3,488	$ 3,546
Interest cost	134	131
Actuarial loss (gain)	17	(104)
Benefit payments	(279)	(85)
Settlement loss	38
Benefit obligation, end of year	3,398	3,488
Other Postretirement Benefit Plan, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit obligation, beginning of year	668	771
Service cost	22	23
Interest cost	28	30
Actuarial loss (gain)	(170)	(147)
Benefit payments	(8)	(9)
Benefit obligation, end of year	$ 540	$ 668