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STOCKHOLDERS' EQUITY - Narrative (Details) |  |  | 1 Months Ended | 2 Months Ended | 6 Months Ended | 12 Months Ended |  |  |  |
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Aug. 09, 2019 USD ($) shares | Feb. 01, 2019 USD ($) shares | Dec. 31, 2019 USD ($) $ / shares shares | May 31, 2019 USD ($) shares | Sep. 30, 2019 USD ($) shares | Jun. 30, 2017 class | Dec. 31, 2019 USD ($) $ / shares shares | Dec. 31, 2018 USD ($) $ / shares shares | May 16, 2019 USD ($) | Apr. 07, 2016 shares | Jan. 12, 2016 USD ($) | Jul. 28, 2015 USD ($)
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Number of classes of stock | class |  |  |  |  |  | 2 |  |  |  |  |  |
Preferred stock, shares authorized (in shares) |  |  | 5,000,000 |  |  |  | 5,000,000 | 5,000,000 |  |  |  |
Preferred stock, par value (in dollars per share) | $ / shares |  |  | $ 0.001 |  |  |  | $ 0.001 | $ 0.001 |  |  |  |
Common stock, shares authorized (in shares) |  |  | 50,000,000 |  |  |  | 50,000,000 | 50,000,000 |  |  |  |
Common stock, par value (in dollars per share) | $ / shares |  |  | $ 0.001 |  |  |  | $ 0.001 | $ 0.001 |  |  |  |
Authorized amount of shares to be repurchased | $ |  |  |  |  |  |  |  |  | $ 8,000,000.0 |  | $ 70,000,000.0 | $ 15,000,000.0
Total purchase price of common stock repurchased | $ |  |  |  | $ 4,700,000 |  |  | $ 10,117,000 |  |  |  |  |
Repurchase of common stock (in shares) |  |  | 97,785 | 612,729 | 383,127 |  |  |  |  |  |  |
Aggregate price of common stock repurchased | $ |  |  | $ 552,000 | $ 6,700,000 | $ 2,900,000 |  | 10,117,000 | $ 0 |  |  |  |
Remaining authorized repurchase amount | $ |  |  | $ 21,900,000 |  |  |  | $ 21,900,000 |  |  |  |  |
Restricted Stock | 2016 Plan |  |  |  |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Number of shares granted (in shares) | 1,117,485 | 22,603 |  |  |  |  | 1,140,088 | 34,202 |  |  |  |
Value of shares granted | $ | $ 7,900,000 | $ 377,000 |  |  |  |  |  |  |  |  |  |
Shares vesting period | 3 years | 3 years |  |  |  |  |  |  |  |  |  |
Common Stock | 2016 Plan |  |  |  |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Number of shares authorized (in shares) |  |  |  |  |  |  |  |  |  | 2,500,000 |  |
Number of shares available for issuance (in shares) |  |  | 1,219,583 |  |  |  | 1,219,583 |  |  |  |  |
Director |  |  |  |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Percentage of common stock outstanding (more than) |  |  |  |  |  |  |  |  | 5.00% |  |  |

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