Income taxes - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
U.S. net operating loss carryforwards (federal and state)	$ 703,125	$ 546,098
Tax credit carryforwards (federal and state)	281,687	246,742
Capitalized license fees and research and development expenses	2,237	1,558
Deferred revenue	604	398
Stock-based compensation	25,181	37,164
Lease liabilities	22,916	14,787
Accruals and other	15,598	12,894
Total deferred tax assets	1,051,348	859,641
Right-of-use assets	(23,053)	(15,044)
Fixed assets	(1,546)	(1,212)
Less valuation allowance	(1,026,749)	(843,385)
Net deferred taxes	$ 0	$ 0