Income Taxes - Reconciliation of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance-beginning of year	$ 104,295	$ 99,470	$ 95,236
Increases based on tax positions of the current year	7,061	8,986	8,926
Reductions due to lapse in statutes of limitations	(3,695)	(4,161)	(4,692)
Balance-end of year	$ 107,661	$ 104,295	$ 99,470