Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Valuation allowance		$ 361,614	$ 242,415
Research and development tax credits		53,472	30,138
Cash paid for income taxes		3,608	4,983	$ 19,727
Gross unrecognized tax benefits	[1]	86,331	66,875	$ 53,213	$ 4,330
Unrecognized tax benefits, reduction to deferred tax assets		84,700	63,100
Unrecognized tax benefits that would impact effective tax rate		1,600	3,800
Other Liabilities, Non current
Gross unrecognized tax benefits		86,300	$ 66,900
Federal
Operating loss carryforwards		5,400
Net operating loss carryforwards subject to expire		$ 900
Net operating loss carryforwards expiration year		2037
Net operating loss carryforward indefinitely		$ 4,500
Research and development tax credits		51,200
State
Operating loss carryforwards		53,100
Research and development tax credits		$ 28,000
State | Beginning Year to Expire
Net operating loss carryforwards expiration year		2040
Foreign
Operating loss carryforwards		$ 592,400
Research and development tax credits		900
UNITED KINGDOM
Valuation allowance		119,200
International
Unremitted earnings of subsidiaries, foreign		3,200
Cash paid for income taxes		$ 0

[1] Includes the impact of a statutory rate change in the U.K