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Stock-based Compensation - Employee Stock Purchase Plan (Details) - USD ($) $ in Thousands | 1 Months Ended | 12 Months Ended |
--- | --- | --- | ---
May 31, 2017 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | May 18, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Proceeds from issuance of common stock, net of offering costs |  | $ 170,456 | $ 118,657 | $ 103,259 |
2016 Employee Stock Purchase Plan |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Share-based compensation, number of shares authorized (in shares) |  |  |  |  | 800,000
Maximum employee contribution percent | 10.00% |  |  |  |
Percent of fair market value to purchase shares | 85.00% |  |  |  |
Common stock purchased by employees (in shares) |  | 32,430 |  |  |
Proceeds from issuance of common stock, net of offering costs |  | $ 600 |  |  |

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- Definition Number of shares authorized for issuance under share-based payment arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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