Employee Benefit Plans - Net Defined Benefit Plan Costs (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Compensation And Retirement Disclosure [Abstract]
Service costs	$ 2,742	$ 2,358	$ 5,669	$ 4,331
Interest costs	1,274	1,269	2,631	2,341
Amortization of actuarial loss	617	280	1,268	597
Expected return on plan assets	(1,117)	(691)	(2,298)	(1,324)
Net defined benefit plan costs	$ 3,516	$ 3,216	$ 7,270	$ 5,945