Employee Benefit Plans - Obligation and Funded Status of Defined Benefit Pension Plan and Retirement Plan (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Change in benefit obligation
Benefit obligation at beginning of year	$ 31,510	$ 33,299
Service cost	531	785	$ 693
Interest cost	1,367	1,350	1,278
Actuarial loss (gain)	1,132	(2,599)
Benefits paid	(1,386)	(1,325)
Ending benefit obligation (December 31)	33,154	31,510	33,299
Change in plan assets
Fair value of plan assets at beginning of year	19,933	19,725
Return on assets	1,551	(296)
Employer contribution	1,917	1,829
Benefits paid	(1,386)	(1,325)
Fair value of plan assets at end of year	22,015	19,933	19,725
Funded status (underfunded)	(11,139)	(11,577)
Amounts recognized in the consolidated balance sheet
Current liabilities	545	527
Non-current liabilities	10,595	11,050
Unrecognized loss included in accumulated other comprehensive loss
Unrecognized loss before tax, beginning balance	8,919	10,614
Amortization	(762)	(887)	(419)
Liability (gain) loss	1,132	(2,599)
Asset (loss) gain	(69)	1,791
Unrecognized loss before tax, ending balance	9,220	8,919	$ 10,614
Tax impact	(3,425)	(3,316)
Unrecognized loss included in accumulated other comprehensive loss, net of tax	$ 5,795	$ 5,603