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Stockholders' Equity - Common Stock (Details) - USD ($) |  |  |  | 3 Months Ended | 7 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Sep. 21, 2018 | Jul. 25, 2018 | Jun. 01, 2018 | Dec. 31, 2018 | Dec. 31, 2018 | Dec. 31, 2019 | Dec. 31, 2018 | May 24, 2018 | May 23, 2018
Common Stock [Abstract] |  |  |  |  |  |  |  |  |
Number of shares callable by warrants (in shares) |  |  |  |  |  |  |  | 2,300,000 | 23,400,000
Proceeds from sale of common stock, net |  |  |  |  |  | $ 15,964,000 | $ 0 |  |
Common stock issued, value |  |  |  |  |  | $ 2,208,000 | $ 1,624,000 |  |
Series U Warrants [Member] |  |  |  |  |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |  |  |  |  |
Common stock issued (in shares) |  |  |  |  |  | 3,450,000 |  |  |
Sale of Stock, Price Per Share |  |  |  |  |  | $ 5.00 |  |  |
Warrants expected term |  |  |  |  |  | 5 years |  |  |
Representative Warrants [Member] |  |  |  |  |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |  |  |  |  |
Number of shares callable by warrants (in shares) |  |  |  |  |  | 75,000 |  |  |
Warrant exercise price (in dollars per share) |  |  |  |  |  | $ 6.25 |  |  |
Common Stock [Member] |  |  |  |  |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |  |  |  |  |
Common stock issued (in shares) |  | 6,723 |  |  |  | 184,666 | 92,169 |  |
Warrants expected term |  |  |  |  |  | 5 years |  |  |
Common Stock [Member] | B. Riley FBR [Member] | Sales Agreement [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |  |  |  |  |
Proceeds from sale of common stock, net |  |  | $ 6,500,000 |  |  |  |  |  |
Common Stock [Member] | B. Riley FBR [Member] | ATM Program [Member] | Sales Agreement [Member] |  |  |  |  |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |  |  |  |  |
Common stock issued (in shares) |  |  |  |  | 79,234 |  |  |  |
Proceeds from sale of common stock, net |  |  |  |  | $ 1,700,000 |  |  |  |
Common Stock [Member] | B. Riley FBR [Member] | ATM Program [Member] | Sales Agreement [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |  |  |  |  |
Proceeds from sale of common stock, net |  |  | $ 6,500,000 |  |  |  |  |  |
Common Stock [Member] | Lincoln Park Capital Fund, LLC [Member] |  |  |  |  |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |  |  |  |  |
Common stock issued (in shares) |  |  |  |  |  | 32,170 |  |  |
Proceeds from sale of common stock, net |  |  |  |  |  | $ 300,000 |  |  |
Common stock issued, value | $ 5,000,000 |  |  |  |  |  |  |  |
Period exercisable from the date of issuance | 24 months |  |  |  |  |  |  |  |
Common Stock [Member] | Lincoln Park Capital Fund, LLC [Member] | Purchase Agreement [Member] |  |  |  |  |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |  |  |  |  |
Common stock issued (in shares) |  |  |  | 12,802 |  |  |  |  |
Proceeds from sale of common stock, net |  |  |  | $ 300,000 |  |  |  |  |
Common Class A [Member] |  |  |  |  |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |  |  |  |  |
Common stock issued (in shares) |  |  |  |  |  | 289,000 |  |  |
Common Class B [Member] |  |  |  |  |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |  |  |  |  |
Number of shares callable by warrants (in shares) |  |  |  |  |  | 2,711,000 |  |  |

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