Income Taxes - Reconciliation of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$ 39,356	$ 43,418
Additions based on tax positions related to the current year	3,155	2,941
Reductions for tax positions of prior years	(5,694)	(7,003)
Settlements	0	0
Balance at end of year	$ 36,817	$ 39,356