SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Held to maturity Investments) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	$ 82,789
Gross Unrealized Gains	194
Gross Unrealized Losses	(202)
Estimated Fair Market Value	82,781
Investments due in less than 3 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	15,947
Gross Unrealized Gains	9
Gross Unrealized Losses	(1)
Estimated Fair Market Value	15,955
Investments due in 4-12 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	34,801
Gross Unrealized Gains	180
Gross Unrealized Losses	(23)
Estimated Fair Market Value	34,958
Investments due in more than 12 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	32,041
Gross Unrealized Gains	5
Gross Unrealized Losses	(178)
Estimated Fair Market Value	31,868
Commercial paper [Member] | Investments due in less than 3 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	9,849
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Estimated Fair Market Value	9,849
Corporate securities [Member] | Investments due in less than 3 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	6,098
Gross Unrealized Gains	9
Gross Unrealized Losses	(1)
Estimated Fair Market Value	6,106
Corporate securities [Member] | Investments due in 4-12 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	24,801
Gross Unrealized Gains	179
Gross Unrealized Losses	(23)
Estimated Fair Market Value	24,957
Corporate securities [Member] | Investments due in more than 12 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	32,041
Gross Unrealized Gains	5
Gross Unrealized Losses	(178)
Estimated Fair Market Value	31,868
Certificates of Deposit [Member] | Investments due in 4-12 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	10,000
Gross Unrealized Gains	1
Gross Unrealized Losses	0
Estimated Fair Market Value	$ 10,001