Redeemable Convertible Preferred Stock Warrants - Schedule of Share based Payment Award, Stock Options, Valuation Assumptions (Details)	9 Months Ended	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividends	0.00%	0.00%
Expected volatility maximum	75.90%	75.20%
Expected volatility minimum	72.90%	61.60%
Risk-free interest rate maximum	1.10%	0.70%
Risk-free interest rate minimum	0.60%	0.30%
Warrants For Series D Redeemable Convertible Preferred Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividends	0.00%		0.00%
Expected volatility maximum	55.00%		52.40%
Expected volatility minimum	51.30%		48.20%
Risk-free interest rate maximum	1.40%		0.80%
Risk-free interest rate minimum	1.10%		0.60%
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected warrant life	6 years 1 month 6 days	6 years 1 month 6 days
Maximum \| Warrants For Series D Redeemable Convertible Preferred Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected warrant life	7 years 9 months 18 days		8 years 7 months 6 days
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected warrant life	5 years	5 years
Minimum \| Warrants For Series D Redeemable Convertible Preferred Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected warrant life	5 years 7 months 6 days		6 years 4 months 24 days

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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- Definition

The estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

No definition available.

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The estimated measure of the minimum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

No definition available.

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- Definition

The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

No definition available.

+ Details

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The minimum risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=122041274&loc=d3e301413-122809

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