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Stock Incentive Plan and Other Equity Activity (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 | Mar. 31, 2021 | Sep. 30, 2020 | Jun. 30, 2020 | Mar. 31, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Sale of Stock [Line Items] |  |  |  |  |  |  |
Stock-based compensation expense | $ 1,840 |  | $ 1,765 |  |  | $ 5,690 | $ 7,961
Shares withheld for taxes | $ (99) | $ (5,619) | (133) | $ (50) | $ (772) |  |
Shares issued from exercise of warrants (in shares) | 125,000 |  |  |  |  | 125,000 |
Number of warrants exercised (in shares) | 230,000 |  |  |  |  | 230,000 |
Fair value of warrants exercised | $ 2,812 |  |  |  |  | $ 2,812 |
Employee Stock Purchase Plan | ESPP |  |  |  |  |  |  |
Sale of Stock [Line Items] |  |  |  |  |  |  |
Stock-based compensation expense | $ 19 |  | $ 18 |  |  | $ 66 | $ 54
Treasury Stock |  |  |  |  |  |  |
Sale of Stock [Line Items] |  |  |  |  |  |  |
Shares withheld for taxes (in shares) |  | 16,000 | 14,000 | 3,000 | 46,000 |  |
Shares withheld for taxes |  | $ (296) | $ (133) | $ (32) | $ (668) |  |
Treasury Stock | RSU/PSU |  |  |  |  |  |  |
Sale of Stock [Line Items] |  |  |  |  |  |  |
Shares withheld for taxes (in shares) | 4,000 |  |  |  |  | 250,000 |
Shares withheld for taxes | $ 99 |  |  |  |  | $ 5,718 |

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