FAIR VALUE MEASUREMENT AND MARKETABLE SECURITIES (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Schedule of cost aggregate fair value and unrealized holding gains and losses by major security

	As of December 31, 2016
	U.S. dollars in thousands
	Level 1		Level 2		Total
Cash equivalent – Money market funds		6,123		—		6,123
U.S. government treasuries		22,893		—		22,893
Corporate debt securities		—		329,337		329,337
		29,016		329,337		358,353

	As of December 31, 2015
	U.S. dollars in thousands
	Level 1		Level 2		Total
Cash equivalent – Money market funds		1,986		—		1,986
U.S. government treasuries		10,874		—		10,874
Corporate debt securities		—		309,502		309,502
		12,860		309,502		322,362

Schedule of aggregate fair value and gross unrealized gains and losses by major security

	As of December 31, 2016
	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses		Aggregate fair value
	U.S. dollars in thousands
U.S. government treasuries		22,939		12		58		22,893
Corporate debt securities		330,015		140		818		329,337
		352,954		152		876		352,230

	As of December 31, 2015
	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses		Aggregate fair value
	U.S. dollars in thousands
U.S. government treasuries		10,898		1		25		10,874
Corporate debt securities		311,253		38		1,789		309,502
		322,151		39		1,814		320,376

Schedule of contractual maturities of investments in available for sale debt securities

​	Adjusted cost as of December 31, 2016
Due in 1 year	​	121,608
Due in 2 years	​	154,240
Due in 3 years	​	57,316
Due in 4 years	​	19,790
​	​	352,954