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]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	$ 82,789
Held-to-maturity Securities, Unrecognized Holding Gain	194
Held-to-maturity Securities, Unrecognized Holding Loss	(202)
Held-to-maturity Securities, Fair Value	82,781
Investments due in less than 3 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	15,947
Held-to-maturity Securities, Unrecognized Holding Gain	9
Held-to-maturity Securities, Unrecognized Holding Loss	(1)
Held-to-maturity Securities, Fair Value	15,955
Investments due in 4-12 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	34,801
Held-to-maturity Securities, Unrecognized Holding Gain	180
Held-to-maturity Securities, Unrecognized Holding Loss	(23)
Held-to-maturity Securities, Fair Value	34,958
Investments due in more than 12 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	32,041
Held-to-maturity Securities, Unrecognized Holding Gain	5
Held-to-maturity Securities, Unrecognized Holding Loss	(178)
Held-to-maturity Securities, Fair Value	31,868
Commercial paper [Member] | Investments due in less than 3 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	9,849
Held-to-maturity Securities, Unrecognized Holding Gain	0
Held-to-maturity Securities, Unrecognized Holding Loss	0
Held-to-maturity Securities, Fair Value	9,849
Corporate securities [Member] | Investments due in less than 3 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	6,098
Held-to-maturity Securities, Unrecognized Holding Gain	9
Held-to-maturity Securities, Unrecognized Holding Loss	(1)
Held-to-maturity Securities, Fair Value	6,106
Corporate securities [Member] | Investments due in 4-12 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	24,801
Held-to-maturity Securities, Unrecognized Holding Gain	179
Held-to-maturity Securities, Unrecognized Holding Loss	(23)
Held-to-maturity Securities, Fair Value	24,957
Corporate securities [Member] | Investments due in more than 12 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	32,041
Held-to-maturity Securities, Unrecognized Holding Gain	5
Held-to-maturity Securities, Unrecognized Holding Loss	(178)
Held-to-maturity Securities, Fair Value	31,868
Certificates of deposit [Member] | Investments due in 4-12 months [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	10,000
Held-to-maturity Securities, Unrecognized Holding Gain	1
Held-to-maturity Securities, Unrecognized Holding Loss	0
Held-to-maturity Securities, Fair Value	$ 10,001