Employee Benefit Plans - Obligation and Funded Status of Defined Benefit Pension Plan and Retirement Plan (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Change in benefit obligation
Benefit obligation at beginning of year	$ 33,299	$ 28,438
Service cost	785	693	$ 843
Interest cost	1,350	1,278	1,160
Actuarial (gain) loss	(2,599)	4,117
Benefits paid	(1,325)	(1,227)
Ending benefit obligation (December 31)	31,510	33,299	28,438
Change in plan assets
Fair value of plan assets at beginning of year	19,725	18,367
Return on assets	(296)	669
Employer contribution	1,829	1,916
Benefits paid	(1,325)	(1,227)
Fair value of plan assets at end of year	19,933	19,725	18,367
Funded status (under funded)	(11,577)	(13,574)
Amounts recognized in the consolidated balance sheet
Current liabilities	527	464
Non-current liabilities	11,050	13,110
Unrecognized loss included in accumulated other comprehensive loss
Unrecognized loss before tax, beginning balance	10,614	6,183
Amortization	(887)	(419)	(1,093)
Liability (gain) loss	(2,599)	4,117
Asset loss	1,791	733
Unrecognized loss before tax, ending balance	8,919	10,614	$ 6,183
Tax impact	(3,316)	(3,970)
Unrecognized loss included in accumulated other comprehensive loss, net of tax	5,603	6,644
Prepaid benefit cost included in other assets	1,984	1,832
Accrued benefit cost included in other liabilities	$ 4,646	$ 4,795