MARKETABLE SECURITITES Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 96,727	$ 83,866
Gross Unrealized Gains	167	8
Gross Unrealized Losses	(3)	(105)
Estimated Fair Market Value	96,891	83,769
Investments due in less than 3 months:
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	22,216	38,586
Gross Unrealized Gains	0	7
Gross Unrealized Losses	(3)	(10)
Estimated Fair Market Value	22,213	38,583
Investments due in 4-12 months:
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	41,900	33,654
Gross Unrealized Gains	50	1
Gross Unrealized Losses	0	(36)
Estimated Fair Market Value	41,950	33,619
Investments due between 12 months and 5 years:
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	32,611	11,626
Gross Unrealized Gains	117	0
Gross Unrealized Losses	0	(59)
Estimated Fair Market Value	32,728	11,567
Corporate securities | Investments due in less than 3 months:
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,027	38,586
Gross Unrealized Gains	0	7
Gross Unrealized Losses	(3)	(10)
Estimated Fair Market Value	14,024	38,583
Corporate securities | Investments due in 4-12 months:
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	33,591	33,654
Gross Unrealized Gains	50	1
Gross Unrealized Losses	0	(36)
Estimated Fair Market Value	33,641	33,619
Corporate securities | Investments due between 12 months and 5 years:
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	32,611	11,626
Gross Unrealized Gains	117	0
Gross Unrealized Losses	0	(59)
Estimated Fair Market Value	32,728	$ 11,567
Commercial paper | Investments due in less than 3 months:
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,189
Gross Unrealized Gains	0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	0
Estimated Fair Market Value	8,189
Commercial paper | Investments due in 4-12 months:
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,309
Gross Unrealized Gains	0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	0
Estimated Fair Market Value	$ 8,309