MARKETABLE SECURITIES (Schedule of Marketable Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Fair value	$ 14,512	$ 47,220
Israeli mutual funds [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	1,011	991
Certificates of deposit [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	1,589	2,773
U.S. Goverment and agency bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	11,413	25,215
U.S Treasury bills [Member]
Debt Securities, Available-for-sale [Line Items]
Fair value	$ 499	$ 18,241