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Stockholders' Equity - Reserved Shares of Common Stock for Issuance (Details) - shares | Sep. 30, 2021 | Dec. 31, 2020
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Class of Stock [Line Items] |  |
Common stock reserved for future issuance (in shares) | 3,601,238 | 2,725,956
Stock options issued and outstanding |  |
Class of Stock [Line Items] |  |
Common stock reserved for future issuance (in shares) | 183,271 | 255,000
Nonvested restricted stock units issued and outstanding |  |
Class of Stock [Line Items] |  |
Common stock reserved for future issuance (in shares) | 369,614 | 450,614
Stock-based awards available for grant under the 2017 Plan |  |
Class of Stock [Line Items] |  |
Common stock reserved for future issuance (in shares) | 3,048,353 | 2,020,342

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- Definition Aggregate number of common shares reserved for future issuance. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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