Employee Benefit Plans - Summary of Benefit Obligations and Funded Status of the Plan (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Compensation Related Costs [Abstract]
Accumulated benefit obligation at end of year	$ 104,775	$ 99,312
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	109,400	118,261
Service cost	2,799	3,355	$ 2,909
Interest cost	5,094	4,870	4,745
Actuarial (gain) loss	2,569	(13,413)
Acquisition	1,392
Benefits paid	(5,796)	(3,673)
Projected benefit obligation at end of year	115,458	109,400	118,261
Change in fair value of plan assets:
Fair value of plan assets at beginning of year	113,292	110,037
Actual return on plan assets	7,125	(572)
Employer contribution	5,750	7,500	7,500
Acquisition	1,226
Benefits paid	(5,796)	(3,673)
Fair value of plan assets at end of year	121,597	113,292	$ 110,037
Amounts recognized in the statement of financial position:
Funded status	6,139	3,892
Net amounts recognized as receivable pension costs in the consolidated balance sheets	6,139	3,892
Amounts recognized in accumulated other comprehensive income consist of:
Unrecognized prior service cost	130	156
Unrecognized net loss	27,857	27,549
Net amounts recognized in accumulated other comprehensive income (before tax)	$ 27,987	$ 27,705
Weighted average assumptions used to determine benefit obligations:
Discount rate	4.46%	4.74%
Rate of compensation increase	3.74%	3.82%
Expected long-term return on assets	6.30%	6.79%