MARKETABLE SECURITIES (Schedule of the Fair Value to Amortized Cost Basis of Securities Held-to-Maturity) (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Cash equivalents and Short-term marketable securities:
Amortized Cost	$ 242,000
Gross Unrealized Gains	332
Gross Unrealized Losses	(19)
Fair Value	242,313
Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract]
Amortized Cost	53,499
Gross Unrealized Gains	21
Gross Unrealized Losses	0
Fair Value	53,520
Amortized Cost	295,499
Gross Unrealized Gains	353
Gross Unrealized Losses	(19)
Fair Value	295,833
Commercial paper
Cash equivalents and Short-term marketable securities:
Amortized Cost	130,464
Gross Unrealized Gains	17
Gross Unrealized Losses	(9)
Fair Value	130,472
Corporate bonds
Cash equivalents and Short-term marketable securities:
Amortized Cost	85,396
Gross Unrealized Gains	225
Gross Unrealized Losses	(10)
Fair Value	85,611
Agency bonds
Cash equivalents and Short-term marketable securities:
Amortized Cost	26,140
Gross Unrealized Gains	90
Gross Unrealized Losses
Fair Value	$ 26,230