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CASH, CASH EQUIVALENTS AND SHORT AND LONG TERM INVESTMENTS - Summary of Available-for-sale Investments (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items] |  |
Cost |  | $ 2,179
Cash Collection |  | (479)
Impairment charges and equity losses |  | (1,308)
Transfer- out from available- for- sale investments |  | (392)
Level 3 |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Estimated fair value | $ 0 |
Minimum |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Maturity period of bank notes receivable | 3 months |
Maximum |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Maturity period of bank notes receivable | 1 year |
Shares of a private company |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Cost |  | 479
Cash Collection |  | (479)
Convertible bonds of private company |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Cost |  | 800
Impairment charges and equity losses |  | (408)
Transfer- out from available- for- sale investments |  | (392)
Preferred convertible shares of private company |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Cost |  | 900
Impairment charges and equity losses |  | $ (900)

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- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References No definition available. + Details
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