Stock-Based Compensation - Restricted stock award activity (Details) - Restricted Stock Units (RSUs) - $ / shares shares in Thousands |
1 Months Ended | 9 Months Ended | 12 Months Ended | |||
|---|---|---|---|---|---|---|
Sep. 30, 2019 |
Sep. 30, 2017 |
Sep. 30, 2021 |
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
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| Number of Shares | ||||||
| Outstanding beginning balance | 1,261 | 37 | ||||
| Granted | 37 | 75 | 1,720 | 1,510 | ||
| Vested | 322 | 185 | 38 | 38 | ||
| Forfeited | 4 | 101 | ||||
| Outstanding ending balance | 2,655 | 1,261 | 37 | |||
| Expected to vest | 2,330 | 1,149 | ||||
| Weighted Average Grant Date Fair Value | ||||||
| Outstanding beginning balance (in dollars per share) | $ 7.74 | $ 3.72 | ||||
| Granted (in dollars per share) | $ 3.72 | $ 1.68 | 30.88 | 7.59 | ||
| Outstanding ending balance (in dollars per share) | $ 22.54 | $ 7.74 | $ 3.72 | |||
| X | ||||||||||
- Definition Number of outstanding equity instruments other than options expected to vest. No definition available.
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| X | ||||||||||
- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. No definition available.
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| X | ||||||||||
- 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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| X | ||||||||||
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. No definition available.
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| X | ||||||||||
- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Details
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