Stock Based Compensation - Stock Option Valuation (Details) - Stock options	9 Months Ended	12 Months Ended
Sep. 30, 2021	Dec. 31, 2020
Assumptions used to determine the fair value of stock options granted
Risk-free interest rate (as percentage)	0.99%	0.53%
Expected volatility (as percentage)	74.00%	75.00%
Expected term (in years)	6 years 7 days	5 years 11 months 26 days

No definition available.

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- Definition

The estimated measure of the 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.

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- Definition

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

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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.

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-Name Accounting Standards Codification
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