FAIR VALUE MEASUREMENTS (Details) - Recurring Basis - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
ASSETS:
Total assets at fair value	$ 9,640,707	$ 7,143,021
Level 1
ASSETS:
Total assets at fair value	1,076,152	490,952
Level 2
ASSETS:
Total assets at fair value	8,564,555	6,652,069
Cash equivalents | U.S. Treasury money market funds
ASSETS:
Total assets at fair value	99,117	155,608
Cash equivalents | Foreign government securities
ASSETS:
Total assets at fair value	10,659	974,855
Cash equivalents | U.S. government securities
ASSETS:
Total assets at fair value	90,441	676,503
Cash equivalents | Commercial paper
ASSETS:
Total assets at fair value	335,663	382,544
Cash equivalents | U.S. government agency securities
ASSETS:
Total assets at fair value		10,000
Cash equivalents | Corporate debt securities
ASSETS:
Total assets at fair value	1,855	45,340
Cash equivalents | Level 1 | U.S. Treasury money market funds
ASSETS:
Total assets at fair value	99,117	155,608
Cash equivalents | Level 1 | Foreign government securities
ASSETS:
Total assets at fair value	0	0
Cash equivalents | Level 1 | U.S. government securities
ASSETS:
Total assets at fair value	0	0
Cash equivalents | Level 1 | Commercial paper
ASSETS:
Total assets at fair value	0	0
Cash equivalents | Level 1 | U.S. government agency securities
ASSETS:
Total assets at fair value		0
Cash equivalents | Level 1 | Corporate debt securities
ASSETS:
Total assets at fair value	0	0
Cash equivalents | Level 2 | U.S. Treasury money market funds
ASSETS:
Total assets at fair value	0	0
Cash equivalents | Level 2 | Foreign government securities
ASSETS:
Total assets at fair value	10,659	974,855
Cash equivalents | Level 2 | U.S. government securities
ASSETS:
Total assets at fair value	90,441	676,503
Cash equivalents | Level 2 | Commercial paper
ASSETS:
Total assets at fair value	335,663	382,544
Cash equivalents | Level 2 | U.S. government agency securities
ASSETS:
Total assets at fair value		10,000
Cash equivalents | Level 2 | Corporate debt securities
ASSETS:
Total assets at fair value	1,855	45,340
Short-term Investments | Foreign government securities
ASSETS:
Total assets at fair value	395,797	52,490
Short-term Investments | U.S. government securities
ASSETS:
Total assets at fair value	456,494	364,266
Short-term Investments | Commercial paper
ASSETS:
Total assets at fair value	11,688	39,092
Short-term Investments | U.S. government agency securities
ASSETS:
Total assets at fair value	2,007	104,811
Short-term Investments | Corporate debt securities
ASSETS:
Total assets at fair value	305,260	581,523
Short-term Investments | Level 1 | Foreign government securities
ASSETS:
Total assets at fair value	0	0
Short-term Investments | Level 1 | U.S. government securities
ASSETS:
Total assets at fair value	0	0
Short-term Investments | Level 1 | Commercial paper
ASSETS:
Total assets at fair value	0	0
Short-term Investments | Level 1 | U.S. government agency securities
ASSETS:
Total assets at fair value	0	0
Short-term Investments | Level 1 | Corporate debt securities
ASSETS:
Total assets at fair value	0	0
Short-term Investments | Level 2 | Foreign government securities
ASSETS:
Total assets at fair value	395,797	52,490
Short-term Investments | Level 2 | U.S. government securities
ASSETS:
Total assets at fair value	456,494	364,266
Short-term Investments | Level 2 | Commercial paper
ASSETS:
Total assets at fair value	11,688	39,092
Short-term Investments | Level 2 | U.S. government agency securities
ASSETS:
Total assets at fair value	2,007	104,811
Short-term Investments | Level 2 | Corporate debt securities
ASSETS:
Total assets at fair value	305,260	581,523
Long-term Investments | Foreign government securities
ASSETS:
Total assets at fair value	719,631	12,671
Long-term Investments | U.S. government securities
ASSETS:
Total assets at fair value	578,450	556,448
Long-term Investments | U.S. government agency securities
ASSETS:
Total assets at fair value		95,094
Long-term Investments | U.S. municipal securities
ASSETS:
Total assets at fair value	1,083	1,102
Long-term Investments | Corporate debt securities
ASSETS:
Total assets at fair value	4,276,614	2,329,033
Long-term Investments | Ctrip convertible debt securities
ASSETS:
Total assets at fair value	1,378,550	425,961
Long-term Investments | Ctrip equity securities
ASSETS:
Total assets at fair value	977,035	335,344
Long-term Investments | Level 1 | Foreign government securities
ASSETS:
Total assets at fair value	0	0
Long-term Investments | Level 1 | U.S. government securities
ASSETS:
Total assets at fair value	0	0
Long-term Investments | Level 1 | U.S. government agency securities
ASSETS:
Total assets at fair value		0
Long-term Investments | Level 1 | U.S. municipal securities
ASSETS:
Total assets at fair value	0	0
Long-term Investments | Level 1 | Corporate debt securities
ASSETS:
Total assets at fair value	0	0
Long-term Investments | Level 1 | Ctrip convertible debt securities
ASSETS:
Total assets at fair value	0	0
Long-term Investments | Level 1 | Ctrip equity securities
ASSETS:
Total assets at fair value	977,035	335,344
Long-term Investments | Level 2 | Foreign government securities
ASSETS:
Total assets at fair value	719,631	12,671
Long-term Investments | Level 2 | U.S. government securities
ASSETS:
Total assets at fair value	578,450	556,448
Long-term Investments | Level 2 | U.S. government agency securities
ASSETS:
Total assets at fair value		95,094
Long-term Investments | Level 2 | U.S. municipal securities
ASSETS:
Total assets at fair value	1,083	1,102
Long-term Investments | Level 2 | Corporate debt securities
ASSETS:
Total assets at fair value	4,276,614	2,329,033
Long-term Investments | Level 2 | Ctrip convertible debt securities
ASSETS:
Total assets at fair value	1,378,550	425,961
Long-term Investments | Level 2 | Ctrip equity securities
ASSETS:
Total assets at fair value	0	0
Foreign exchange derivatives
LIABILITIES:
Total liabilities at fair value	644	129
Foreign exchange derivatives | Level 1
LIABILITIES:
Total liabilities at fair value	0	0
Foreign exchange derivatives | Level 2
LIABILITIES:
Total liabilities at fair value	644	129
Foreign exchange derivatives | Short-term Investments
ASSETS:
Total assets at fair value	363	336
Foreign exchange derivatives | Short-term Investments | Level 1
ASSETS:
Total assets at fair value	0	0
Foreign exchange derivatives | Short-term Investments | Level 2
ASSETS:
Total assets at fair value	$ 363	$ 336