SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Short Term and Long Term Investments) (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	$ 63,134	$ 67,758
Gross Unrealized Gains	686	755
Gross Unrealized Losses	0	(1)
Estimated Fair Market Value	63,820	68,512
Commercial paper [Member] | Investments due in less than 3 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost		7,135
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Estimated Fair Market Value		7,135
U.S. government debt securities [Member] | Investments due in less than 3 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	5,026
Gross Unrealized Gains	8
Gross Unrealized Losses	0
Estimated Fair Market Value	5,034
U.S. government debt securities [Member] | Investments due in 4-12 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost		5,095
Gross Unrealized Gains		20
Gross Unrealized Losses		0
Estimated Fair Market Value		5,115
U.S. municipal securities [Member] | Investments due in less than 3 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	1,000
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Estimated Fair Market Value	1,000
U.S. municipal securities [Member] | Investments due in 4-12 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost		1,005
Gross Unrealized Gains		3
Gross Unrealized Losses		0
Estimated Fair Market Value		1,008
Corporate securities [Member] | Investments due in less than 3 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	1,426	1,508
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	(1)
Estimated Fair Market Value	1,426	1,507
Corporate securities [Member] | Investments due in 4-12 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	25,639	21,255
Gross Unrealized Gains	250	84
Gross Unrealized Losses	0	0
Estimated Fair Market Value	25,889	21,339
Corporate securities [Member] | Investments due in more than 12 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	30,043	31,760
Gross Unrealized Gains	428	648
Gross Unrealized Losses	0	0
Estimated Fair Market Value	30,471	32,408
Investments due in less than 3 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	7,452	8,643
Gross Unrealized Gains	8	0
Gross Unrealized Losses	0	(1)
Estimated Fair Market Value	7,460	8,642
Investments due in 4-12 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	25,639	27,355
Gross Unrealized Gains	250	107
Gross Unrealized Losses	0	0
Estimated Fair Market Value	25,889	27,462
Investments due in more than 12 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	30,043	31,760
Gross Unrealized Gains	428	648
Gross Unrealized Losses	0	0
Estimated Fair Market Value	$ 30,471	$ 32,408