Employee Benefit Plans - Changes in Plan Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Changes in plan assets
Fair value of plan assets at beginning of year	$ 2,311,227	$ 2,043,379
Actual return on plan assets	347,560	427,597
Foreign currency exchange rate changes	7,451	9,826
Employer contributions	21,765	15,799
Plan participants’ contributions	1,864	2,246
Benefits paid	(144,508)	(119,789)
Settlements	0	(67,831)
Fair value of plan assets at end of year	$ 2,545,359	$ 2,311,227