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STOCK BASED COMPENSATION - Non-vested Options Outstanding and Exercisable (Details) - $ / shares shares in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward] |  |  |
Stock options granted (in shares) | 338 | 645 |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value |  |  |
Stock options granted (in dollars per share) | $ 2.99 | $ 2.36 | $ 0.49
Amended and Restated Equity Incentive Plan and Non-related Plan Options |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward] |  |  |
Balance at the beginning of the period (in shares) | 2,463 |  |
Stock options granted (in shares) | 392 |  |
Stock options cancelled/forfeited (in shares) | (19) |  |
Stock options vested (in shares) | (1,357) |  |
Balance at the end of the period (in shares) | 1,479 | 2,463 |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value |  |  |
Balance at the beginning of the period (in dollars per share) | $ 1.08 |  |
Stock options granted (in dollars per share) | 1.69 |  |
Stock options cancelled/forfeited (in dollars per share) | 1.85 |  |
Stock options vested (in dollars per share) | 1.08 |  |
Balance at the end of the period (in dollars per share) | $ 1.24 | $ 1.08 |

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- Definition Gross number of share options (or share units) granted during the period. + References No definition available. + Details
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- Definition The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Number of non-vested options outstanding. + References No definition available. + Details
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
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- Definition Weighted average grant-date fair value of non-vested options forfeited. + References No definition available. + Details
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- Definition Number of options vested. + References No definition available. + Details
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