FAIR VALUE MEASUREMENTS (Details) - Recurring Basis [Member] - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
ASSETS:
Total assets at fair value	$ 8,624,835	$ 7,143,021
Foreign Currency Contracts [Member]
LIABILITIES:
Total liabilities at fair value	552	129
Short-term Investments [Member] | Foreign Currency Contracts [Member]
ASSETS:
Total assets at fair value	369	336
Money market funds | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	266,816	155,608
Foreign government securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	211,690	974,855
Foreign government securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	199,461	52,490
Foreign government securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	427,511	12,671
U.S. government securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	341,981	676,503
U.S. government securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	587,863	364,266
U.S. government securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	735,160	556,448
Commercial paper | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	109,384	382,544
Commercial paper | Short-term Investments [Member]
ASSETS:
Total assets at fair value		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	511,803	581,523
Corporate debt securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	3,934,052	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		104,811
U.S. government agency securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	2,018	95,094
U.S. municipal securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	1,104	1,102
Ctrip convertible debt securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	760,399	425,961
Ctrip equity securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	535,224	335,344
Level 1 [Member]
ASSETS:
Total assets at fair value	802,040	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	266,816	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
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
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 convertible 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	535,224	335,344
Level 2 [Member]
ASSETS:
Total assets at fair value	7,822,795	6,652,069
Level 2 [Member] | Foreign Currency Contracts [Member]
LIABILITIES:
Total liabilities at fair value	552	129
Level 2 [Member] | Short-term Investments [Member] | Foreign Currency Contracts [Member]
ASSETS:
Total assets at fair value	369	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	211,690	974,855
Level 2 [Member] | Foreign government securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	199,461	52,490
Level 2 [Member] | Foreign government securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	427,511	12,671
Level 2 [Member] | U.S. government securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	341,981	676,503
Level 2 [Member] | U.S. government securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	587,863	364,266
Level 2 [Member] | U.S. government securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	735,160	556,448
Level 2 [Member] | Commercial paper | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	109,384	382,544
Level 2 [Member] | Commercial paper | Short-term Investments [Member]
ASSETS:
Total assets at fair value		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	511,803	581,523
Level 2 [Member] | Corporate debt securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	3,934,052	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		104,811
Level 2 [Member] | U.S. government agency securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	2,018	95,094
Level 2 [Member] | U.S. municipal securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	1,104	1,102
Level 2 [Member] | Ctrip convertible debt securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	760,399	425,961
Level 2 [Member] | Ctrip equity securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	$ 0	$ 0