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STOCKHOLDERS' EQUITY - Options (Details) $ / shares in Units, shares in Millions, $ in Millions |  | 3 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | --- | ---
Apr. 06, 2017 shares | Jun. 30, 2018 USD ($) shares | Jun. 30, 2017 USD ($) | Jun. 30, 2018 USD ($) $ / shares shares | Jun. 30, 2017 USD ($) $ / shares shares | Dec. 31, 2017 shares | Sep. 09, 2016 shares
General and administrative |  |  |  |  |  |  |
Stock-based compensation |  |  |  |  |  |  |
Compensation expense recorded | $ |  | $ 4.2 | $ 12.9 | $ 7.8 | $ 21.3 |  |
Stock options | Employee |  |  |  |  |  |  |
Stock-based compensation |  |  |  |  |  |  |
Percentage of awards vesting on the annual anniversary date of the grant |  | 33.33 |  | 33.33 |  |  |
Vesting period |  |  |  | 3 years |  |  |
Expiration term |  |  |  | 10 years |  |  |
2016 Incentive Plan | Common Stock |  |  |  |  |  |  |
Stock-based compensation |  |  |  |  |  |  |
Aggregate number of shares available | shares | 19.0 |  |  |  |  |  | 10.0
Maximum number of shares that remained reserved for issuance under the Plan | shares |  | 4.9 |  | 4.9 |  | 7.7 |
Increase in shares available for issuance | shares | 9.0 |  |  |  |  |  |
Number of calculation days for which shares will be available for issuance. | 20 days |  |  |  |  |  |
2016 Incentive Plan | Stock options |  |  |  |  |  |  |
Stock-based compensation |  |  |  |  |  |  |
Weighted average remaining vesting period |  |  |  | 1 year | 1 year 4 months 24 days |  |
Exercise of stock options | $ |  |  |  | $ 0.3 |  |  |
Restricted stock |  |  |  |  |  |  |
Unrecognized compensation expense stock option | $ |  | $ 9.9 | 23.1 | $ 9.9 | $ 23.1 |  |
2016 Incentive Plan | Stock options | Employee |  |  |  |  |  |  |
Number of Shares |  |  |  |  |  |  |
Granted (in shares) | shares |  |  |  | 1.2 | 1.8 |  |
Weighted Average Exercise Price Per Share |  |  |  |  |  |  |
Granted (in dollars per share) |  |  |  | $ 5.65 | $ 7.72 |  |
2016 Incentive Plan | Stock options | Employee | Minimum |  |  |  |  |  |  |
Weighted Average Exercise Price Per Share |  |  |  |  |  |  |
Granted (in dollars per share) |  |  |  |  | 6.55 |  |
2016 Incentive Plan | Stock options | Employee | Maximum |  |  |  |  |  |  |
Weighted Average Exercise Price Per Share |  |  |  |  |  |  |
Granted (in dollars per share) |  |  |  |  | $ 7.75 |  |
2016 Incentive Plan | Restricted Stock |  |  |  |  |  |  |
Stock-based compensation |  |  |  |  |  |  |
Weighted average remaining vesting period |  |  |  | 1 year 6 months | 9 months 18 days |  |
Weighted average grant date price (in dollars per share) |  |  |  | $ 5.53 | $ 7.07 |  |
Unrecognized compensation expense other than options | $ |  | $ 11.0 | $ 13.9 | $ 11.0 | $ 13.9 |  |
2016 Incentive Plan | Restricted Stock | Minimum |  |  |  |  |  |  |
Stock-based compensation |  |  |  |  |  |  |
Grant date price (in dollars per share) |  |  |  | $ 4.00 | $ 6.08 |  |
2016 Incentive Plan | Restricted Stock | Maximum |  |  |  |  |  |  |
Stock-based compensation |  |  |  |  |  |  |
Grant date price (in dollars per share) |  |  |  | $ 5.65 | $ 7.75 |  |
2016 Incentive Plan | Restricted Stock | Employees and non-employee directors |  |  |  |  |  |  |
Number of Shares |  |  |  |  |  |  |
Granted (in shares) | shares |  |  |  | 2.2 | 2.0 |  |
2016 Incentive Plan | Restricted Stock | Employee |  |  |  |  |  |  |
Stock-based compensation |  |  |  |  |  |  |
Percentage of awards other than options vesting on the annual anniversary date of the grant |  |  |  | 33.33% |  |  |
Vesting period |  |  |  | 3 years |  |  |
2016 Incentive Plan | Restricted Stock | Non-employee director |  |  |  |  |  |  |
Stock-based compensation |  |  |  |  |  |  |
Vesting period |  |  |  | 6 months |  |  |

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