Employee Benefits - Summary of Components of Net Pension Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Components of net periodic benefit cost:
Service cost	$ 7,896	$ 6,232
Interest cost	1,269	2,616
Expected return on plan assets	(8,141)	(7,425)
Prior service (credit) cost	(2,946)	6
Recognized net actuarial loss	3,538	2,361
Net periodic benefit cost	$ 1,616	$ 3,790