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Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2018 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2017 | Mar. 31, 2009
Preferred Stock |  |  |  |  |
Preferred stock, Shares authorized | 300,000 |  |  | 300,000 |
Series B Stock |  |  |  |  |
Preferred Stock |  |  |  |  |
Fair value |  |  |  |  | $ 68.2
Shares redeemed (in shares) |  | 73,000 | 73,000 |  |
Warrants |  |  |  |  |
Preferred Stock |  |  |  |  |
Warrants, term | 10 years |  |  |  |
Warrants to purchase the Company's common stock, initially authorized (in shares) | 815,339 |  |  |  |
Warrants, exercise price (in dollars per share) | $ 13.43 |  |  |  |
Fair value |  |  |  |  | $ 4.8

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