Employee Benefit Plans - Obligation and Funded Status of Defined Benefit Pension Plan and Retirement Plan (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in benefit obligation
Benefit obligation at beginning of year	$ 36,002	$ 33,154
Service cost	601	531	$ 531
Interest cost	1,268	1,329	1,367
Actuarial (gain) loss	(2,415)	2,449
Benefits paid	(1,505)	(1,461)
Ending benefit obligation	33,951	36,002	33,154
Change in plan assets
Fair value of plan assets at beginning of year	25,646	22,015
Return on assets	(1,951)	3,481
Employer contribution	1,559	1,611
Benefits paid	(1,505)	(1,461)
Fair value of plan assets at end of year	23,749	25,646	22,015
Funded status (underfunded)	(10,202)	(10,356)
Amounts recognized in the consolidated balance sheet
Current liabilities	580	560
Non-current liabilities	9,622	9,796
Unrecognized loss included in accumulated other comprehensive loss
Unrecognized loss before tax, beginning balance	8,908	9,220
Amortization	(743)	(810)
Liability (gain) loss	(2,415)	2,449
Asset loss (gain)	3,735	(1,951)
Unrecognized loss before tax, ending balance	9,485	8,908	$ 9,220
Tax impact	(2,263)	(3,309)
Unrecognized loss included in accumulated other comprehensive loss, net of tax	$ 7,222	$ 5,599