Income Taxes - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance of unrecognized tax benefits at beginning of year	$ 38,162	$ 26,428	$ 24,198
Gross amount of increases in unrecognized tax benefits as a result of positions taken during a prior year	9,751	1,169	1,254
Gross amount of decreases in unrecognized tax benefits as a result of positions taken during a prior year	(5,362)	(268)	(3)
Gross amount of increases in unrecognized tax benefits as a result of positions taken during the current year	14,677	13,191	8,131
The amounts of decreases in unrecognized benefits relating to settlements with taxing authorities	(4,550)	0	(6,075)
Reduction in unrecognized tax benefits due to the lapse of applicable statute of limitation	(1,725)	(2,358)	(1,077)
Balance of unrecognized tax benefits at end of year	$ 50,953	$ 38,162	$ 26,428