Net Loss Per Share - Schedule of Common Stock Equivalents were Excluded from Computation of Diluted Net Loss per Share (Detail) - shares	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	70,109,359	38,903,476
Unvested RSAs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	1,114,006	2,468,416
Unvested RSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	6,055,931	1,643,312
Unvested Performance-Based RSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	84,505	66,683
Common Stock Options Issued and Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	12,669,110	10,320,564
Estimated Shares Issuable Under Performance-Based Milestone Compensation Arrangements
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	29,396,554	3,785,559
Estimated Shares Issuable Under the ESPP
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	207,960	37,649
Assumed Conversion of 2027 Notes
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	12,878,305	12,878,305
Assumed Conversion of 2029 Notes
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	7,702,988	7,702,988