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SIGNIFICANT ACCOUNTING POLICIES (Marketable Securities) (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Marketable Securities [Line Items] |  |
Total cash equivalents | $ 0 | $ 2,395
Total marketable securities | 51,857 | 42,421
Total | 51,857 | 44,816
U.S. Treasury securities |  |
Marketable Securities [Line Items] |  |
Total marketable securities | 28,901 | 12,406
Corporate notes and bonds |  |
Marketable Securities [Line Items] |  |
Total marketable securities | 22,956 | 26,678
Commercial paper |  |
Marketable Securities [Line Items] |  |
Total marketable securities | 0 | 3,337
Commercial paper |  |
Marketable Securities [Line Items] |  |
Total cash equivalents | $ 0 | $ 2,395

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- Definition Amount of short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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