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SHARE-BASED PAYMENTS - Schedule of Share-based Compensation, Stock Options and Restricted Stock Units Activity (Details) - $ / shares | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Stock-option |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward] |  |  |
Number of nonvested shares, beginning of period (in shares) | 227,178 | 177,698 | 139,600
Granted, nonvested, number of shares (in shares) | 738,893 | 449,537 | 2,176,330
Vested, number of shares (in shares) | (486,386) | (331,482) | (2,119,803)
Nonvested options forfeited, number of shares (in shares) | (114,505) | (68,575) | (18,429)
Number of nonvested shares, end of period (in shares) | 365,180 | 227,178 | 177,698
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] |  |  |
Nonvested, weighted average grant date fair value, beginning of period (in dollars per share) | $ 1.48 | $ 3.44 | $ 5.27
Granted, nonvested, weighted average grant date fair value (in dollars per share) | 1.18 | 1.29 | 1.93
Vested, weighted average grant date fair value (in dollars per share) | 1.30 | 2.26 | 2.00
Nonvested options forfeited, weighted average grant date fair value (in dollars per share) | 1.22 | 1.56 | 5.17
Nonvested, weighted average grant date fair value, end of period (in dollars per share) | $ 1.20 | $ 1.48 | $ 3.44
RSU |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward] |  |  |
Number of nonvested shares, beginning of period (in shares) | 1,330,469 | 272,866 | 0
Granted, nonvested, number of shares (in shares) | 1,390,705 | 1,205,336 | 282,716
Vested, number of shares (in shares) | (752,580) | (138,608) | 0
Nonvested options forfeited, number of shares (in shares) | (59,118) | (9,125) | (9,850)
Number of nonvested shares, end of period (in shares) | 1,909,477 | 1,330,469 | 272,866
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] |  |  |
Nonvested, weighted average grant date fair value, beginning of period (in dollars per share) | $ 2.37 | $ 4.03 | $ 0.00
Granted, nonvested, weighted average grant date fair value (in dollars per share) | 2.09 | 2.14 | 4.05
Vested, weighted average grant date fair value (in dollars per share) | 2.35 | 4.65 | 0.00
Nonvested options forfeited, weighted average grant date fair value (in dollars per share) | 2.29 | 5.39 | 4.68
Nonvested, weighted average grant date fair value, end of period (in dollars per share) | $ 2.17 | $ 2.37 | $ 4.03
Restricted Stock Units (RSUs) |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Number of RSUs granted in period (in shares) | 1,390,000 | 1,210,000 | 280,000

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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + 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 (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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