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