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SHARE-BASED PAYMENTS - Schedule of Share-based Compensation, Outstanding and Exercisable Options (Details) - USD ($) | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of options (in shares) | 1,609,087 | 1,487,433 | 1,732,754 | 2,028,847
Outstanding options, weighted average exercise price (in dollars per share) | $ 2.91 | $ 3.43 | $ 3.84 | $ 4.48
Options outstanding, intrinsic value | $ 2,731,000 |  |  |
Number of exercisable options (in shares) | 1,205,097 |  |  |
Exercisable options, intrinsic value | $ 1,803,000 |  |  |
Minimum |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Outstanding options, weighted average exercise price (in dollars per share) | $ 1.70 | 1.70 | 1.70 | 1.77
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 | $ 15.61 | $ 15.61
$0.00 to $4.99 |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of options (in shares) | 1,449,587 |  |  |
Outstanding options, weighted average exercise price (in dollars per share) | $ 2,410 |  |  |
Options outstanding, weighted average remaining contractual life | 2 years 10 months 28 days |  |  |
Options outstanding, intrinsic value | $ 2,731,000 |  |  |
Number of exercisable options (in shares) | 1,045,597 |  |  |
Exercisable options, weighted average exercise price (in dollars per share) | $ 2,590 |  |  |
Options exercisable, weighted average remaining contractual life | 2 years 7 months 9 days |  |  |
Exercisable options, intrinsic value | $ 1,803,000 |  |  |
$0.00 to $4.99 | Minimum |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Options outstanding, weighted average price (per share) | $ 0 |  |  |
Options exercisable, weighted average price (per share) | 0 |  |  |
$0.00 to $4.99 | Maximum |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Options outstanding, weighted average price (per share) | 4.99 |  |  |
Options exercisable, weighted average price (per share) | $ 4.99 |  |  |
$10.00 to $14.99 |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of options (in shares) | 13,515 |  |  |
Outstanding options, weighted average exercise price (in dollars per share) | $ 12,590 |  |  |
Options outstanding, weighted average remaining contractual life | 3 months 7 days |  |  |
Options outstanding, intrinsic value | $ 0 |  |  |
Number of exercisable options (in shares) | 13,515 |  |  |
Exercisable options, weighted average exercise price (in dollars per share) | $ 12,590 |  |  |
Options exercisable, weighted average remaining contractual life | 3 months 7 days |  |  |
Exercisable options, intrinsic value | $ 0 |  |  |
$10.00 to $14.99 | Minimum |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Options outstanding, weighted average price (per share) | $ 10.00 |  |  |
Options exercisable, weighted average price (per share) | 10.00 |  |  |
$10.00 to $14.99 | Maximum |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Options outstanding, weighted average price (per share) | 14.99 |  |  |
Options exercisable, weighted average price (per share) | $ 14.99 |  |  |
$15.00 to $19.99 |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of options (in shares) | 12,750 |  |  |
Outstanding options, weighted average exercise price (in dollars per share) | $ 15,610 |  |  |
Options outstanding, weighted average remaining contractual life | 10 days |  |  |
Options outstanding, intrinsic value | $ 0 |  |  |
Number of exercisable options (in shares) | 12,750 |  |  |
Exercisable options, weighted average exercise price (in dollars per share) | $ 15,610 |  |  |
Options exercisable, weighted average remaining contractual life | 10 days |  |  |
Exercisable options, intrinsic value | $ 0 |  |  |
$15.00 to $19.99 | Minimum |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Options outstanding, weighted average price (per share) | $ 15.00 |  |  |
Options exercisable, weighted average price (per share) | 15.00 |  |  |
$15.00 to $19.99 | Maximum |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Options outstanding, weighted average price (per share) | 19.99 |  |  |
Options exercisable, weighted average price (per share) | $ 19.99 |  |  |
$5.00 to $9.99 |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of options (in shares) | 133,235 |  |  |
Outstanding options, weighted average exercise price (in dollars per share) | $ 6,160 |  |  |
Options outstanding, weighted average remaining contractual life | 1 year 6 months 7 days |  |  |
Options outstanding, intrinsic value | $ 0 |  |  |
Number of exercisable options (in shares) | 133,235 |  |  |
Exercisable options, weighted average exercise price (in dollars per share) | $ 6,160 |  |  |
Options exercisable, weighted average remaining contractual life | 1 year 6 months 7 days |  |  |
Exercisable options, intrinsic value | $ 0 |  |  |
$5.00 to $9.99 | Minimum |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Options outstanding, weighted average price (per share) | $ 5.00 |  |  |
Options exercisable, weighted average price (per share) | 5.00 |  |  |
$5.00 to $9.99 | Maximum |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Options outstanding, weighted average price (per share) | 9.99 |  |  |
Options exercisable, weighted average price (per share) | $ 9.99 |  |  |

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