FAIR VALUE MEASUREMENTS (Details) - Recurring Basis [Member] - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
ASSETS:
Total assets at fair value	$ 14,536,412	$ 13,055,008
Foreign Currency Contracts [Member]
ASSETS:
Total assets at fair value	558	756
LIABILITIES:
Total liabilities at fair value	593	1,015
Money market funds | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	1,249,091	977,468
International government securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	35,052	30,266
International government securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	518,465	249,684
International government securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	451,551	659,344
U.S. government securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	159,956	176,140
U.S. government securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	580,220	456,888
U.S. government securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	822,319	766,592
Commercial paper | Cash Equivalents [Member]
ASSETS:
Total assets at fair value		1,998
Commercial paper | Short-term Investments [Member]
ASSETS:
Total assets at fair value	5,978	1,998
Time deposits | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	4,724	49,160
Corporate debt securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	10,243	9,273
Corporate debt securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	1,831,495	1,510,310
Corporate debt securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	6,360,199	6,001,789
U.S. government agency securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	4,946	4,952
Ctrip convertible debt securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	1,438,375	1,293,088
Ctrip equity securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	1,063,240	865,302
Level 1 [Member]
ASSETS:
Total assets at fair value	2,317,055	1,891,930
Level 1 [Member] | Foreign Currency Contracts [Member]
ASSETS:
Total assets at fair value	0	0
LIABILITIES:
Total liabilities at fair value	0	0
Level 1 [Member] | Money market funds | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	1,249,091	977,468
Level 1 [Member] | International government securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 [Member] | International government securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 [Member] | International 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
Level 1 [Member] | Commercial paper | Short-term Investments [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 [Member] | Time deposits | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	4,724	49,160
Level 1 [Member] | Corporate debt securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	0	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 | 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	1,063,240	865,302
Level 2 [Member]
ASSETS:
Total assets at fair value	12,219,357	11,163,078
Level 2 [Member] | Foreign Currency Contracts [Member]
ASSETS:
Total assets at fair value	558	756
LIABILITIES:
Total liabilities at fair value	593	1,015
Level 2 [Member] | Money market funds | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	0	0
Level 2 [Member] | International government securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	35,052	30,266
Level 2 [Member] | International government securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	518,465	249,684
Level 2 [Member] | International government securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	451,551	659,344
Level 2 [Member] | U.S. government securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	159,956	176,140
Level 2 [Member] | U.S. government securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	580,220	456,888
Level 2 [Member] | U.S. government securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	822,319	766,592
Level 2 [Member] | Commercial paper | Cash Equivalents [Member]
ASSETS:
Total assets at fair value		1,998
Level 2 [Member] | Commercial paper | Short-term Investments [Member]
ASSETS:
Total assets at fair value	5,978	1,998
Level 2 [Member] | Time deposits | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	0	0
Level 2 [Member] | Corporate debt securities | Cash Equivalents [Member]
ASSETS:
Total assets at fair value	10,243	9,273
Level 2 [Member] | Corporate debt securities | Short-term Investments [Member]
ASSETS:
Total assets at fair value	1,831,495	1,510,310
Level 2 [Member] | Corporate debt securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	6,360,199	6,001,789
Level 2 [Member] | U.S. government agency securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	4,946	4,952
Level 2 [Member] | Ctrip convertible debt securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	1,438,375	1,293,088
Level 2 [Member] | Ctrip equity securities | Long-term Investments [Member]
ASSETS:
Total assets at fair value	$ 0	$ 0