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Capital Structure - Series A Preferred Stock (Details) $ / shares in Units, $ in Millions |  | 12 Months Ended
--- | --- | ---
Feb. 15, 2018 USD ($) member $ / shares shares | Dec. 31, 2017 vote
Series A Preferred Stock |  |
Class of Stock [Line Items] |  |
Number of votes per share (vote) | vote |  | 1
Subsequent Event |  |
Class of Stock [Line Items] |  |
Preferred stock, dividend rate percentage | 14.50% |
Convertible preferred stock, shares issued upon conversion | shares | 0.0555556 |
Convertible preferred stock, conversion price per share | $ / shares | $ 18.00 |
Ten Percent or Greater Ownership | Subsequent Event |  |
Class of Stock [Line Items] |  |
Number of elected directors | member | 2 |
Preferred stock, ownership percentage | 10.00% |
Greater than Five and Less than Ten Percent Ownership | Subsequent Event |  |
Class of Stock [Line Items] |  |
Number of elected directors | member | 1 |
Greater than Five and Less than Ten Percent Ownership | Subsequent Event | Minimum |  |
Class of Stock [Line Items] |  |
Preferred stock, ownership percentage | 5.00% |
Greater than Five and Less than Ten Percent Ownership | Subsequent Event | Maximum |  |
Class of Stock [Line Items] |  |
Preferred stock, ownership percentage | 10.00% |
EBITDA Non-Compliance | Subsequent Event | Silver Private Holdings I, LLC |  |
Class of Stock [Line Items] |  |
Fair value approval threshold | $ 10.0 |
Fair market value of transaction, individual | 5.0 |
Fair market value of transaction, aggregate | 10.0 |
Capital expenditure threshold | $ 25.0 |
Conversion of Stock | Subsequent Event | Silver Private Holdings I, LLC |  |
Class of Stock [Line Items] |  |
Percentage ownership after conversion | 19.90% |
Voting percentage threshold of ownership | 19.99% |

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