Income Taxes - Schedule of Changes in Gross Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Unrecognized tax benefits, beginning balance	$ 163,980	$ 160,040	$ 151,100
Additions based on tax positions related to current	5,879	4,355	8,598
Additions for tax positions of prior years	1,888	815	427
Reductions for tax positions of prior years	(322)	(1,230)	(31)
Decreases related to settlements of prior year tax positions			(54)
Unrecognized tax benefits, ending balance	$ 171,425	$ 163,980	$ 160,040