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SUBSEQUENT EVENTS (Details) - USD ($) $ / shares in Units, $ in Thousands |  | 2 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jan. 23, 2018 | Mar. 08, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Subsequent Event [Line Items] |  |  |  |  |
Stock options granted in period (in shares) |  |  | 738,893 | 449,537 | 2,176,330
Grants in period, weighted average exercise price (in dollars per share) |  |  | $ 2.34 | $ 2.13 | $ 6.02
Subsequent Event |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |
Grants in period, weighted average exercise price (in dollars per share) | $ 1.70 |  |  |  |
Employee Stock Option |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |
Stock options granted in period (in shares) |  |  | 740,000 | 450,000 |
Employee Stock Option | Subsequent Event |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |
Stock options granted in period (in shares) | 420,000 |  |  |  |
Employee Stock Option | Share-based Compensation Award, Tranche One | Subsequent Event |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |
Award vesting rights, percentage | 50.00% |  |  |  |
Employee Stock Option | Share-based Compensation Award, Tranche Two | Subsequent Event |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |
Award vesting rights, percentage | 25.00% |  |  |  |
Employee Stock Option | Share-based Compensation Award, Tranche Three | Subsequent Event |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |
Award vesting rights, percentage | 25.00% |  |  |  |
Restricted Stock Units (RSUs) |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |
Shares granted in share-based compensation awards (in shares) |  |  | 1,390,000 | 1,210,000 | 280,000
Restricted Stock Units (RSUs) | Subsequent Event |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |
Shares granted in share-based compensation awards (in shares) | 880,000 |  |  |  |
Restricted Stock Units (RSUs) | Share-based Compensation Award, Tranche Four | Subsequent Event |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |
Award vesting rights, percentage | 50.00% |  |  |  |
Restricted Stock Units (RSUs) | Share-based Compensation Award, Tranche Five | Subsequent Event |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |
Award vesting rights, percentage | 25.00% |  |  |  |
Restricted Stock Units (RSUs) | Share-based Compensation Award, Tranche Six | Subsequent Event |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |
Award vesting rights, percentage | 25.00% |  |  |  |
At The Market Sale Of Stock |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |
Sale of stock, number of shares issued (in shares) |  |  | 200,225 | 1,275,908 |
Sale of stock consideration received |  |  | $ 14,550 | $ 540 | $ 2,940
At The Market Sale Of Stock | Subsequent Event |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |
Sale of stock, number of shares issued (in shares) |  | 390,000 |  |  |
Sale of stock consideration received |  | $ 650 |  |  |

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