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SIGNIFICANT ACCOUNTING POLICIES (Marketable Securities) (Details) - USD ($) $ in Thousands | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Marketable Securities [Line Items] |  |
Total cash equivalents | $ 2,395 | $ 8,126
Short-term marketable securities | 42,421 | 52,856
Total financial assets | 44,816 | 60,982
Total marketable securities and cash equivalents | 44,816 | 60,982
U.S. Treasury securities |  |
Marketable Securities [Line Items] |  |
Short-term marketable securities | 12,406 | 10,133
Corporate notes and bonds |  |
Marketable Securities [Line Items] |  |
Short-term marketable securities | 26,678 | 38,036
Commercial paper |  |
Marketable Securities [Line Items] |  |
Short-term marketable securities | 3,337 | 4,687
Commercial paper |  |
Marketable Securities [Line Items] |  |
Total cash equivalents | $ 2,395 | $ 8,126

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