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Stockholders' Equity (At-the-Market) (Details) - At The Market - USD ($) $ / shares in Units, $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Aug. 16, 2019
Class of Stock [Line Items] |  |  |
At-the-market, maximum potential proceeds |  |  | $ 400,000
Sales commission, percent of gross sales price |  |  | 2.00%
Number of shares issued (in shares) | 0 | 1,357,526 |
Value remaining outstanding for future offerings | $ 390,000 |  |
Gross proceeds (usd per share) |  | $ 7.40 |
Proceeds from sale of stock |  | $ 9,900 |
Debt issuance fees |  | $ 100 |

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