| CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (PARENTHETICAL) - USD ($) $ in Thousands | 12 Months Ended | ||
|---|---|---|---|
| Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | |
| Other comprehensive income (loss), available-for-sale securities, before reclassification adjustments, tax | |||
| Unrealized holding gains on available-for-sale debt securities, tax | $ 0 | $ 0 | $ 0 | 
| Reclassification from accumulated other comprehensive income of losses on available-for-sale debt securities included in net loss, tax | $ 0 | $ 0 | $ 0 | 
| X | ||||||||||
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- References No definition available. 
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| X | ||||||||||
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- Definition Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- Definition Amount of tax expense (benefit) before reclassification adjustments of unrealized holding gain (loss) on available-for-sale securities. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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