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SUBSEQUENT EVENTS (Details) - USD ($) $ / shares in Units, $ in Thousands |  |  | 2 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | ---
Feb. 20, 2020 | Jan. 23, 2020 | Mar. 13, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Subsequent Event [Line Items] |  |  |  |  |  |  |
Stock options granted in period (in shares) |  |  |  | 296,450 | 442,956 | 738,893 |
Exercise price (in USD per share) |  |  |  | $ 2.27 | $ 2.15 | $ 0.00 |
Shares issued (in shares) |  |  |  | 100,735,889 | 91,445,066 | 74,366,824 | 66,205,153
Employee Stock Option |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |
Stock options granted in period (in shares) |  |  |  | 300,000 | 420,000 | 740,000 |
Award vesting period |  |  |  | 2 years |  |  |
Employee Stock Option | Subsequent Event |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |
Stock options granted in period (in shares) |  | 570,000 |  |  |  |  |
Exercise price (in USD per share) |  | $ 1.76 |  |  |  |  |
Award vesting period |  | 5 years |  |  |  |  |
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) |  |  |  | 730,000 | 1,190,000 | 1,390,000 |
Award vesting period |  |  |  | 3 years |  |  |
Restricted Stock Units (RSUs) | Subsequent Event |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |
Shares granted in share-based compensation awards (in shares) |  | 740,000 |  |  |  |  |
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 consideration received |  |  |  | $ 19,680 | $ 31,520 | $ 14,150 |
At The Market Sale Of Stock | Subsequent Event |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |
Shares issued (in shares) |  |  | 2,390,000 |  |  |  |
Sale of Stock, Price Per Share |  |  | $ 1.69 |  |  |  |
Sale of stock consideration received |  |  | $ 3,960 |  |  |  |
Public Offering | Subsequent Event |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |
Shares issued (in shares) | 11,300,000 |  |  |  |  |  |
Sale of Stock, Price Per Share | $ 1.47 |  |  |  |  |  |
Sale of stock consideration received | $ 15,070 |  |  |  |  |  |

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