FAIR VALUE MEASUREMENTS (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Level 1 [Member] | Money Market Funds [Member]
Fair value of assets	$ 1,767	$ 6,163	$ 6,510
Level 2 [Member] | Derivative Financial Instruments, Assets [Member]
Fair value of assets			19
Level 2 [Member] | Short-term corporate bonds [Member]
Fair value of assets	110,385	68,272	71,719
Level 2 [Member] | Short-term governmental bonds [Member]
Fair value of assets	8,295	8,992	2,746
Level 2 [Member] | Long-term corporate bonds [Member]
Fair value of assets	74,256	95,160	39,279
Level 2 [Member] | Long-term governmental bonds [Member]
Fair value of assets		7,960	4,983
Level 3 [Member] | Long-term Earn-out provision [Member]
Fair value of liabilities	(332)
Level 3 [Member] | Derivative instruments, liability [Member]
Fair value of liabilities		$ (180)