SIGNIFICANT ACCOUNTING POLICIES (Available-for-sale Investments) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 40,298
Gross Unrealized Loss	(71)
Gross Unrealized Gain	0
Fair Value	40,227
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,048
Gross Unrealized Loss	0
Gross Unrealized Gain	0
Fair Value	2,048
Total cash equivalents
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,048
Gross Unrealized Loss	0
Gross Unrealized Gain	0
Fair Value	2,048
U.S. Treasury securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,865
Gross Unrealized Loss	(10)
Gross Unrealized Gain	0
Fair Value	3,855
Corporate notes and bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	32,790
Gross Unrealized Loss	(61)
Gross Unrealized Gain	0
Fair Value	32,729
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,595
Gross Unrealized Loss	0
Gross Unrealized Gain	0
Fair Value	1,595
Total short-term marketable securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	38,250
Gross Unrealized Loss	(71)
Gross Unrealized Gain	0
Fair Value	$ 38,179