Employee Benefit Plans - Net Periodic Pension Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 688	$ 722	$ 2,196	$ 2,152
Interest cost	1,121	1,301	3,172	3,874
Expected return on plan assets	(3,000)	(2,658)	(8,881)	(7,917)
Recognized net actuarial loss	1,903	1,458	5,064	4,342
Net periodic pension cost	$ 712	$ 823	$ 1,551	$ 2,451
Weighted-average assumptions:
Discount rate	2.81%	3.42%	2.81%	3.42%
Expected return on assets	6.25%	6.75%	6.25%	6.75%
Prior to Age 40 [Member]
Weighted-average assumptions:
Rate of compensation increase	5.00%	5.00%	5.00%	5.00%
Ages 40 to 54 [Member]
Weighted-average assumptions:
Rate of compensation increase	4.00%	4.00%	4.00%	4.00%
Otherwise [Member]
Weighted-average assumptions:
Rate of compensation increase	3.50%	3.50%	3.50%	3.50%