Employee Benefit Plans - Net Periodic Pension Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 715	$ 561	$ 1,430	$ 1,116
Interest cost	1,286	1,459	2,573	2,901
Expected return on plan assets	(2,630)	(2,356)	(5,259)	(4,686)
Recognized net actuarial loss	1,442	1,184	2,884	2,355
Net periodic pension cost	$ 813	$ 848	$ 1,628	$ 1,686
Weighted-Average Assumptions:
Discount Rate	3.42%	4.52%	3.42%	4.52%
Expected return on assets	6.75%	7.00%	6.75%	7.00%
Prior to Age 40 [Member]
Weighted-Average Assumptions:
Rate of compensation increase	5.00%		5.00%
Ages 40 to 54 [Member]
Weighted-Average Assumptions:
Rate of compensation increase	4.00%		4.00%
Prior to Age 45 [Member]
Weighted-Average Assumptions:
Rate of compensation increase		3.50%		3.50%
Otherwise [Member]
Weighted-Average Assumptions:
Rate of compensation increase	3.50%	3.00%	3.50%	3.00%