| STOCKHOLDERS' EQUITY - Equity Offerings (Details) - USD ($) $ / shares in Units, $ in Thousands | 1 Months Ended | 8 Months Ended | 12 Months Ended | 17 Months Ended | |||||
|---|---|---|---|---|---|---|---|---|---|
| Oct. 31, 2017 | May 31, 2017 | Feb. 28, 2017 | Aug. 31, 2015 | Dec. 31, 2017 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2016 | |
| Controlled Equity Offering | |||||||||
| Aggregate proceeds | $ 114,180 | $ 23,586 | $ 5,292 | ||||||
| Common stock | |||||||||
| Controlled Equity Offering | |||||||||
| Number of shares of common stock sold (in shares) | 20,815,000 | 23,000,000 | 2,166,093 | 45,981,093 | 7,895,563 | 1,722,312 | 9,617,875 | ||
| Share price (in dollars per share) | $ 3.35 | $ 2.00 | |||||||
| Aggregate proceeds | $ 65,300 | $ 43,000 | $ 5,700 | $ 30,000 | |||||
| Value of common stock shares registered for sale | $ 0 | $ 0 | |||||||
| Cantor | Common stock | |||||||||
| Controlled Equity Offering | |||||||||
| Maximum value of shares available under Controlled Equity Offering | $ 40,000 | $ 30,000 | |||||||
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- Definition Value of shares available for issuance. No definition available. 
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- Definition Represents information about the Controlled Equity Offering. No definition available. 
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- Definition Maximum value of shares available for sale under a controlled equity offering agreement. No definition available. 
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- Definition The cash inflow from the additional capital contribution to the entity. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Per share or per unit amount of equity securities issued. No definition available. 
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- Definition Number of new stock issued during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Details 
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- Details 
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