FAIR VALUE OF CERTAIN FINANCIAL ASSETS AND LIABILITIES (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Fair value amounts included in the carrying value of
Cash and cash equivalents	$ 359,331	$ 354,842	$ 328,349	$ 256,801
Short-term investments	411,282	244,649
Investments	23,194	44,189
Level 1
Fair value amounts included in the carrying value of
Cash and cash equivalents	311,908	311,202
Short-term investments	8,034	66,522
Total	319,942	377,724
Level 2
Fair value amounts included in the carrying value of
Cash and cash equivalents	47,423	43,640
Short-term investments	390,590	154,064
Total	438,013	197,704
Level 3
Fair value amounts included in the carrying value of
Short-term investments	12,658	24,063
Investments	23,194	44,189
Prepaid expenses and other current assets	873	2,983
Other assets	2,168	785
Total	38,893	72,020
Total fair value
Fair value amounts included in the carrying value of
Cash and cash equivalents	359,331	354,842
Short-term investments	411,282	244,649
Investments	23,194	44,189
Prepaid expenses and other current assets	873	2,983
Other assets	2,168	785
Total	$ 796,848	$ 647,448