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Stockholders' Equity - Preferred Stock (Details) - USD ($) |  |  |  |  | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Sep. 25, 2019 | Aug. 02, 2019 | Jul. 25, 2018 | Jul. 17, 2018 | Dec. 31, 2019 | Dec. 31, 2018 | Aug. 06, 2019 | Aug. 05, 2019 | May 24, 2018 | May 23, 2018
Preferred Stock [Abstract] |  |  |  |  |  |  |  |  |  |
Preferred stock, shares authorized (in shares) |  |  |  |  | 5,000,000 | 5,000,000 | 5,000,000 | 5,000,000 | 5,000,000 | 5,000,000
Preferred stock, par value (in dollars per share) |  |  |  |  | $ 0.001 | $ 0.001 |  |  |  |
Preferred stock, shares outstanding (in shares) |  |  |  |  | 1,959 | 4,606 |  |  |  |
Number of shares callable by warrants (in shares) |  |  |  |  |  |  |  |  | 2,300,000 | 23,400,000
2018 Rights Offering [Member] |  |  |  |  |  |  |  |  |  |
Preferred Stock [Abstract] |  |  |  |  |  |  |  |  |  |
Number of shares callable by warrants (in shares) | 1 |  |  | 1 |  |  |  |  |  |
Common stock issued (in shares) |  |  | 6,723 |  |  |  |  |  |  |
Gross proceeds from private placement of stock |  |  | $ 5,700,000 |  |  |  |  |  |  |
2018 Rights Offering [Member] | Outstanding Warrants [Member] |  |  |  |  |  |  |  |  |  |
Preferred Stock [Abstract] |  |  |  |  |  |  |  |  |  |
Number of shares callable by warrants (in shares) |  |  |  | 1,050 |  |  |  |  |  |
Warrant exercise price (in dollars per share) |  |  |  | $ 1,000 |  |  |  |  |  |
Series A Convertible Preferred Stock [Member] |  |  |  |  |  |  |  |  |  |
Preferred Stock [Abstract] |  |  |  |  |  |  |  |  |  |
Preferred stock, shares outstanding (in shares) |  |  |  |  | 0 | 0 |  |  |  |
Convertible preferred stock |  |  |  |  | 3.60% | 3.60% |  |  |  |
Series B Convertible Preferred Stock [Member] |  |  |  |  |  |  |  |  |  |
Preferred Stock [Abstract] |  |  |  |  |  |  |  |  |  |
Preferred stock, shares outstanding (in shares) |  |  |  |  | 1,021 | 1,112 |  |  |  |
Series C Convertible Preferred Stock [Member] |  |  |  |  |  |  |  |  |  |
Preferred Stock [Abstract] |  |  |  |  |  |  |  |  |  |
Preferred stock, shares authorized (in shares) |  |  | 7,000 |  |  |  |  |  |  |
Preferred stock, par value (in dollars per share) |  |  | $ 0.001 |  |  |  |  |  |  |
Preferred stock, shares outstanding (in shares) |  |  |  |  | 938 | 3,494 |  |  |  |
Common stock issued (in shares) |  |  | 6,723 |  |  |  |  |  |  |
Preferred stock conversion price (in dollars per share) |  |  |  |  | $ 39.93 |  |  |  |  |
Preferred stock conversion price reduced (in dollars per share) |  |  |  |  | $ 7.50 |  |  |  |  |
Series C Convertible Preferred Stock [Member] | Dividend Paid [Member] |  |  |  |  |  |  |  |  |  |
Preferred Stock [Abstract] |  |  |  |  |  |  |  |  |  |
Dividends payable |  | $ 554,000 |  |  | $ 554,000 | $ 2,500,000 |  |  |  |
Series C Convertible Preferred Stock [Member] | 2018 Rights Offering [Member] |  |  |  |  |  |  |  |  |  |
Preferred Stock [Abstract] |  |  |  |  |  |  |  |  |  |
Number of shares callable by warrants (in shares) |  |  |  | 20,000 |  |  |  |  |  |
Preferred stock conversion price (in dollars per share) | $ 7.50 | $ 39.93 |  |  |  |  |  |  |  |
Preferred stock conversion price reduced (in dollars per share) | 3.2132 | $ 7.50 |  |  |  |  |  |  |  |
Common Stock and Series B Convertible Preferred Stock [Member] | 2018 Rights Offering [Member] |  |  |  |  |  |  |  |  |  |
Preferred Stock [Abstract] |  |  |  |  |  |  |  |  |  |
Charge on Non Transferable Subscription Rights |  |  |  | $ 0 |  |  |  |  |  |
Series T Warrants [Member] | 2018 Rights Offering [Member] |  |  |  |  |  |  |  |  |  |
Preferred Stock [Abstract] |  |  |  |  |  |  |  |  |  |
Number of shares callable by warrants (in shares) |  | 1 |  |  |  |  |  |  |  |
Warrant exercise price (in dollars per share) |  | $ 0.7986 |  |  |  |  |  |  |  |
Warrant exercise price reduced (in dollars per share) |  | $ 0.15 |  |  |  |  |  |  |  |
Series T Warrants [Member] | 2018 Rights Offering [Member] | Outstanding Warrants [Member] |  |  |  |  |  |  |  |  |  |
Preferred Stock [Abstract] |  |  |  |  |  |  |  |  |  |
Number of shares callable by warrants (in shares) |  | 50 |  |  |  |  |  |  |  |
Warrant exercise price (in dollars per share) | $ 3.2132 |  |  |  |  |  |  |  |  |
50 Series T Warrants [Member] | 2018 Rights Offering [Member] |  |  |  |  |  |  |  |  |  |
Preferred Stock [Abstract] |  |  |  |  |  |  |  |  |  |
Warrant exercise price (in dollars per share) |  | $ 7.50 |  |  |  |  |  |  |  |
2018 Rights Offering [Member] | Series T Warrants [Member] | Outstanding Warrants [Member] |  |  |  |  |  |  |  |  |  |
Preferred Stock [Abstract] |  |  |  |  |  |  |  |  |  |
Class of warrant outstanding |  |  |  |  | 3,788,400 |  |  |  |  |
Number of warrants exercised |  |  |  |  | 75,768 |  |  |  |  |
2018 Rights Offering [Member] | Series C Convertible Preferred Stock [Member] |  |  |  |  |  |  |  |  |  |
Preferred Stock [Abstract] |  |  |  |  |  |  |  |  |  |
Preferred stock, shares outstanding (in shares) |  |  |  |  | 938 |  |  |  |  |
Number of preferred stock, shares exercised |  |  |  |  | 291,920 |  |  |  |  |

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