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FAIR VALUE MEASUREMENTS - EQUITY INVESTMENT (Details) - Equity Investment - USD ($) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2019 | Mar. 31, 2018 | Dec. 31, 2007
Equity Investments [Line Item] |  |  |
Number of shares owned |  |  | 13,842,625
Cost method investments cost basis |  |  | $ 0
Fair value of equity investment | $ 688,000 |  |
Increase (decrease) in fair value of equity investment | 98,000 | $ (108,000) |
Gain (loss) related to foreign currency translation | $ 5,000 | $ (17,000) |

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