Stockholders' Equity (Common Stock Reserved for Future Issuance) (Details) shares in Thousands	Sep. 30, 2021 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock options outstanding (in shares)	9,727
Total common shares reserved for future issuance (in shares)	91,616
Common stock available for future grant under 2019 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for future grant (in shares)	853
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for future grant (in shares)	260
RSUs outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs outstanding (in shares)	446
Class A-1 convertible preferred stock outstanding (as-converted)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock, shares outstanding (in shares)	2,567
Class A-2 convertible preferred stock outstanding (as-converted)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock, shares outstanding (in shares)	13,308
Class A-3 convertible preferred stock outstanding (as-converted)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock, shares outstanding (in shares)	2,587
2019 PIPE Initial Closing warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants outstanding (in shares)	12,778
2019 PIPE Milestone Closing warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants outstanding (in shares)	30,595
2020 PIPE warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants outstanding (in shares)	18,495

Number of warrants or rights outstanding.

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Aggregate number of common shares reserved for future issuance.

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Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.

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Number of equity instruments other than options outstanding, including both vested and non-vested instruments.

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Number of options outstanding, including both vested and non-vested options.

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