Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities not Included in Calculation of Diluted Net Loss Per Share (Details) - shares shares in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	3,656	6,366
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	0	5,906
Warrant | Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	0	9
Warrant | Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	0	8
Common Stock Options Issued and Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	3,545	230
Common Stock Subject to Repurchase or Forfeiture
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	92	213
ESPP Shares Pending Issuance
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	19	0