Stock-based Compensation - Restricted Stock Awards - Additional Disclosures (Details) - Restricted Stock Awards - USD ($) $ / shares in Units, $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Stock-based Compensation | |||
| Weighted average grant date fair value (in dollars per share) | $ 4.00 | $ 7.30 | $ 18.77 |
| Unrecognized expenses | $ 0.2 | ||
| Weighted-average remaining recognition period (in years) | 4 months 24 days | ||