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SHARE-BASED PAYMENTS - Narrative (Details) - USD ($) | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Mar. 31, 2018 | Mar. 31, 2017 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Number of options (in shares) | 2,355,690 |  | 2,028,847 |  | 2,045,143
Outstanding options, weighted average exercise price (in dollars per share) | $ 3.76 |  | $ 4.48 |  | $ 5.69
Number of grants in period, net of forfeitures (in shares) | 422,956 |  | 738,893 |  |
Share-based compensation | $ 1,200,000 | $ 1,040,000 |  |  |
Stock Incentive Plan |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Common stock, shares authorized (in shares) | 7,597,727 |  |  |  |
Employee Stock Option |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Award vesting period | 2 years |  |  |  |
Award exercise period | 5 years |  |  |  |
Exercisable options, weighted average remaining contractual term | 3 years 8 months 23 days |  |  |  |
Number of grants in period (in shares) | 420,000 | 730,000 |  |  |
Number of options (in shares) | 2,360,000 |  |  |  |
Number of exercisable options (in shares) | 1,780,000 |  |  |  |
Outstanding options, weighted average exercise price (in dollars per share) | $ 3.76 |  |  |  |
Exercisable options, weighted average exercise price (in dollars per share) | $ 4.30 |  |  |  |
Options, vested and expected to Vest, aggregate intrinsic value | $ 8,459 |  |  |  |
Restricted Stock Units (RSUs) |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Award vesting period | 3 years |  |  |  |
Number of grants in period, net of forfeitures (in shares) | 1,190,000 | 1,130,000 |  |  |
Grants in period, grant date intrinsic value (in dollars per share) | $ 2,410,000 | $ 1,640,000 |  |  |
Unrecognized compensation costs related to unvested stock options | $ 240,000 |  |  |  |
Unrecognized compensation costs related to RSU awards | $ 2,350,000 |  |  |  |
Share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition | 2 years |  |  |  |
Maximum |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Outstanding options, weighted average exercise price (in dollars per share) | $ 15.61 |  | $ 15.61 | $ 32.10 |
Maximum | Employee Stock Option |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Exercisable options, weighted average remaining contractual term | 10 years |  |  |  |

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