FAIR VALUE OF CERTAIN FINANCIAL ASSETS AND LIABILITIES (Details 2) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Fair value amounts included in the carrying value of
Cash and cash equivalents	$ 287,019	$ 222,514	$ 283,054	$ 359,331
Short-term investments	315,572	97,042
Investments	9,725	21,393
Asset transfers between Level 1 and Level 2 measurements	0	0
Level 1
Fair value amounts included in the carrying value of
Cash and cash equivalents	244,734	211,087
Total	244,734	211,087
Level 2
Fair value amounts included in the carrying value of
Cash and cash equivalents	42,285	11,427
Short-term investments	308,574	95,279
Total	350,859	106,706
Level 3
Fair value amounts included in the carrying value of
Short-term investments	6,998	1,763
Investments	9,725	21,393
Prepaid expenses and other current assets	729	225
Other assets	790	1,704
Total	18,242	25,085
Total fair value
Fair value amounts included in the carrying value of
Cash and cash equivalents	287,019	222,514
Short-term investments	315,572	97,042
Investments	9,725	21,393
Prepaid expenses and other current assets	729	225
Other assets	790	1,704
Total	$ 613,835	$ 342,878