MARKETABLE SECURITIES (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Amortized Cost
Amortized cost	$ 58,909	$ 41,348
Gross Unrealized Gains
Gross Unrealized Gains	164	147
Gross Unrealized Losses
Gross Unrealized Losses	8	82
Fair Value
Fair Value	59,065	41,413
U.S. government and municipal obligations
Amortized Cost
Maturing in one year or less	15,566	19,993
Maturing after one year through three years	19,797	10,808
Amortized cost	35,363	30,801
Gross Unrealized Gains
Maturing in one year or less	28	20
Maturing after one year through three years	99	122
Gross Unrealized Gains	127	142
Gross Unrealized Losses
Maturing after one year through three years	1	6
Gross Unrealized Losses	1	6
Fair Value
Maturing in one year or less	15,594	20,013
Maturing after one year through three years	19,895	10,924
Fair Value	35,489	30,937
Corporate debt securities
Amortized Cost
Maturing in one year or less	17,353	5,817
Maturing after one year through three years	6,193	4,730
Amortized cost	23,546	10,547
Gross Unrealized Gains
Maturing in one year or less	23	3
Maturing after one year through three years	14	2
Gross Unrealized Gains	37	5
Gross Unrealized Losses
Maturing in one year or less	4	4
Maturing after one year through three years	3	72
Gross Unrealized Losses	7	76
Fair Value
Maturing in one year or less	17,372	5,816
Maturing after one year through three years	6,204	4,660
Fair Value	$ 23,576	$ 10,476