Stock-Based Compensation - Employee Stock Purchase Plan, Valuation Assumptions (Details) - Employee Stock - $ / shares |
9 Months Ended | |
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Sep. 30, 2021 |
Sep. 30, 2020 |
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| Common stock purchased under the ESPP (in shares) | 113,510 | 161,171 |
| Weighted average price of stock purchased under the ESPP (in dollars per share) | $ 23.21 | $ 13.29 |
| Weighted Average Grant Date Fair Value (in dollars per share) | $ 10.85 | $ 6.41 |
| Risk-free interest rate | 0.04% | 0.15% |
| Dividend yield | 0.00% | 0.00% |
| Expected life (in years) | 6 months | 6 months 3 days |
| Volatility | 61.10% | 93.25% |
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- Definition Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition 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. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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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. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition The risk-free interest rate assumption that is used in valuing an option on its own shares. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Per share weighted-average price paid for shares purchased on open market for issuance under share-based payment arrangement. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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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. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Number of shares issued during the period as a result of an employee stock purchase plan. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Details
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