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SUBSEQUENT EVENT (Details) - USD ($) | 1 Months Ended | 3 Months Ended | 6 Months Ended
--- | --- | --- | ---
Jul. 31, 2019 | Jun. 30, 2019 | Jun. 30, 2018 | Mar. 31, 2018 | Jun. 30, 2019 | Jun. 30, 2018
Subsequent Event [Line Items] |  |  |  |  |  |
Issuance of common stock in connection with at market offering, net of issuance costs |  | $ 101,000 | $ 82,306,000 | $ 1,553,000 |  |
2018 Sales Agreement |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |
Issuance of common stock in connection with at market offering, net of issuance costs (in shares) |  | 108,386 | 9,447,026 |  | 108,386 | 9,447,026
Issuance of common stock in connection with at market offering, net of issuance costs |  | $ 101,000 | $ 36,208,000 |  | $ 101,000 | $ 36,208,000
Subsequent Event | 2018 Sales Agreement |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |
Issuance of common stock in connection with at market offering, net of issuance costs (in shares) | 1,784,705 |  |  |  |  |
Issuance of common stock in connection with at market offering, net of issuance costs | $ 2,471,000 |  |  |  |  |

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