Stock-based Compensation - ESPP (Details)  | 
9 Months Ended | 
|---|---|
Sep. 30, 2021  | |
| 2015 ESPP [Member] | |
| Share-based compensation | |
| Percentage related to employees to purchase shares at the lower fair market value at offering period | 85.00% | 
| X | ||||||||||
- 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. No definition available. 
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| X | ||||||||||
- Definition Purchase price of common stock expressed as a percentage of its fair value. No definition available. 
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| X | ||||||||||
- Details 
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