MARKETABLE SECURITIES (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Amortized Cost
Amortized cost	$ 133,499	$ 58,909
Gross Unrealized Gains
Gross Unrealized Gains	104	164
Gross Unrealized Losses
Gross Unrealized Losses	(22)	(8)
Fair Value
Fair Value	133,581	59,065
Marketable securities considered to be other-than-temporarily impaired	0
U.S. government and municipal obligations
Amortized Cost
Maturing in one year or less	55,531	15,566
Maturing after one year through three years	18,234	19,797
Amortized cost	73,765	35,363
Gross Unrealized Gains
Maturing in one year or less	27	28
Maturing after one year through three years	56	99
Gross Unrealized Gains	83	127
Gross Unrealized Losses
Maturing in one year or less	(4)
Maturing after one year through three years	(4)	(1)
Gross Unrealized Losses	(8)	(1)
Fair Value
Maturing in one year or less	55,554	15,594
Maturing after one year through three years	18,286	19,895
Fair Value	73,840	35,489
Corporate debt securities
Amortized Cost
Maturing in one year or less	38,973	17,353
Maturing after one year through three years	20,761	6,193
Amortized cost	59,734	23,546
Gross Unrealized Gains
Maturing in one year or less	9	23
Maturing after one year through three years	12	14
Gross Unrealized Gains	21	37
Gross Unrealized Losses
Maturing in one year or less	(9)	(4)
Maturing after one year through three years	(5)	(3)
Gross Unrealized Losses	(14)	(7)
Fair Value
Maturing in one year or less	38,973	17,372
Maturing after one year through three years	20,768	6,204
Fair Value	$ 59,741	$ 23,576