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Stockholders' Equity - Narrative (Details) $ / shares in Units, $ in Thousands |  | 1 Months Ended | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | ---
Dec. 31, 2016 USD ($) $ / shares shares | Nov. 30, 2017 $ / shares shares | Dec. 31, 2017 USD ($) shares | Dec. 31, 2016 USD ($) $ / shares | Sep. 30, 2017 USD ($) $ / shares shares | Sep. 30, 2016 USD ($) shares | Sep. 30, 2015 executive $ / shares shares | May 31, 2017 shares | Mar. 31, 2017 shares
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Shares issued (in dollars per share) | $ 27.15 |  |  | $ 27.15 |  |  |  |  |
Period of consecutive trading days | 20 days |  |  |  |  |  |  |  |
Period following an executive's termination of employment for a number of reasons | 18 months |  |  |  |  |  |  |  |
Shares of common stock authorized to be repurchased (up to) (in shares) | shares |  |  | 477,500 |  | 7,000,000 | 50,000 |  | 2,000,000 | 5,000,000
Corporate, General and Administrative Expense |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Stock-based compensation expense | $ |  |  | $ 192 | $ 255 |  |  |  |  |
Remy W. Trafelet |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Options granted in period (in shares) | shares | 300,000 |  |  |  |  |  |  |  |
Henry R. Slack |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Options granted in period (in shares) | shares | 225,000 |  |  |  |  |  |  |  |
Tranche One |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Percentage of options | 25.00% |  |  |  |  |  |  |  |
Amount per share (in dollars per share) | $ 60.00 |  |  |  |  |  |  |  |
Tranche Two |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Percentage of options | 25.00% |  |  |  |  |  |  |  |
Amount per share (in dollars per share) | $ 75.00 |  |  |  |  |  |  |  |
Tranche Three |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Percentage of options | 25.00% |  |  |  |  |  |  |  |
Amount per share (in dollars per share) | $ 90.00 |  |  |  |  |  |  |  |
Tranche Four |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Percentage of options | 25.00% |  |  |  |  |  |  |  |
Amount per share (in dollars per share) | $ 105.00 |  |  |  |  |  |  |  |
Restricted Stock |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Stock-based compensation expense | $ |  |  |  |  | $ 26 | $ 150 |  |  |
Restricted shares awarded (in shares) | shares |  | 5,000 |  |  |  |  | 12,500 |  |
Number of senior executives | executive |  |  |  |  |  |  | 2 |  |
Weighted average fair value (in dollars per share) |  | $ 31.95 |  |  |  |  | $ 49.49 |  |
Award vesting period |  | 3 years |  |  |  |  |  |  |
Unrecognized expense | $ | $ 413 |  | 283 | 413 |  |  |  |  |
Employee Stock Option |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Stock-based compensation expense | $ |  |  | $ 205 | $ 0 |  |  |  |  |
Unrecognized expense | $ |  |  |  |  | $ 1,822 | $ 2,646 |  |  |
Weighted average remaining contractual term |  |  | 2 years 3 months 19 days |  |  |  |  |  |
Weighted average grant date fair value of option grants (in dollars per share) |  |  |  |  | $ 3.53 |  |  |  |
Minimum | Restricted Stock |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Award vesting period |  |  |  |  |  |  | 3 years |  |
Maximum | Restricted Stock |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Award vesting period |  |  |  |  |  |  | 5 years |  |

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