FAIR VALUE MEASUREMENTS (Details) - Recurring Basis [Member] - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014
ASSETS:
Total assets at fair value	$ 8,489,781	$ 7,143,021
Foreign Currency Contracts [Member]
LIABILITIES:
Total liabilities at fair value	493	129
Short-term Investments [Member] | Foreign Currency Contracts [Member]
ASSETS:
Total assets at fair value	374	336
Money market funds | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	286,477	155,608
Foreign government securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	386,404	974,855
Foreign government securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	141,266	52,490
Foreign government securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	311,254	12,671
U.S. government securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	1,241,506	676,503
U.S. government securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	655,744	364,266
U.S. government securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	701,517	556,448
Commercial paper | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	221,735	382,544
Commercial paper | Short-term Investments [Member]
ASSETS:
Total assets at fair value	32,198	39,092
Corporate debt securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value		45,340
Corporate debt securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	545,810	581,523
Corporate debt securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	3,042,667	2,329,033
U.S. government agency securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value		10,000
U.S. government agency securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	4,623	104,811
U.S. government agency securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	2,546	95,094
U.S. municipal securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	1,107	1,102
Ctrip corporate debt securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	482,512	425,961
Ctrip equity securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	432,041	335,344
Level 1 [Member]
ASSETS:
Total assets at fair value	718,518	490,952
Level 1 [Member] | Foreign Currency Contracts [Member]
LIABILITIES:
Total liabilities at fair value	0	0
Level 1 [Member] | Short-term Investments [Member] | Foreign Currency Contracts [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 [Member] | Money market funds | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	286,477	155,608
Level 1 [Member] | Foreign government securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 [Member] | Foreign government securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 [Member] | Foreign government securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 [Member] | U.S. government securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 [Member] | U.S. government securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 [Member] | U.S. government securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 [Member] | Commercial paper | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 [Member] | Commercial paper | Short-term Investments [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 [Member] | Corporate debt securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value		0
Level 1 [Member] | Corporate debt securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 [Member] | Corporate debt securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 [Member] | U.S. government agency securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value		0
Level 1 [Member] | U.S. government agency securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 [Member] | U.S. government agency securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 [Member] | U.S. municipal securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 [Member] | Ctrip corporate debt securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 [Member] | Ctrip equity securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	432,041	335,344
Level 2 [Member]
ASSETS:
Total assets at fair value	7,771,263	6,652,069
Level 2 [Member] | Foreign Currency Contracts [Member]
LIABILITIES:
Total liabilities at fair value	493	129
Level 2 [Member] | Short-term Investments [Member] | Foreign Currency Contracts [Member]
ASSETS:
Total assets at fair value	374	336
Level 2 [Member] | Money market funds | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	0	0
Level 2 [Member] | Foreign government securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	386,404	974,855
Level 2 [Member] | Foreign government securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	141,266	52,490
Level 2 [Member] | Foreign government securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	311,254	12,671
Level 2 [Member] | U.S. government securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	1,241,506	676,503
Level 2 [Member] | U.S. government securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	655,744	364,266
Level 2 [Member] | U.S. government securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	701,517	556,448
Level 2 [Member] | Commercial paper | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	221,735	382,544
Level 2 [Member] | Commercial paper | Short-term Investments [Member]
ASSETS:
Total assets at fair value	32,198	39,092
Level 2 [Member] | Corporate debt securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value		45,340
Level 2 [Member] | Corporate debt securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	545,810	581,523
Level 2 [Member] | Corporate debt securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	3,042,667	2,329,033
Level 2 [Member] | U.S. government agency securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value		10,000
Level 2 [Member] | U.S. government agency securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	4,623	104,811
Level 2 [Member] | U.S. government agency securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	2,546	95,094
Level 2 [Member] | U.S. municipal securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	1,107	1,102
Level 2 [Member] | Ctrip corporate debt securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	482,512	425,961
Level 2 [Member] | Ctrip equity securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	$ 0	$ 0