FAIR VALUE MEASUREMENTS Fair value measurements (Details) - Recurring Basis - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
ASSETS:
Total assets at fair value	$ 11,679	$ 13,681
Foreign Currency Contracts
ASSETS:
Total assets at fair value	1	4
LIABILITIES:
Total liabilities at fair value	2
Other Long-term Investments [Member]
ASSETS:
Total assets at fair value	200	200
Money market funds | Cash Equivalents
ASSETS:
Total assets at fair value	1,727	2,061
International government securities | Cash Equivalents
ASSETS:
Total assets at fair value		21
International government securities | Short-term Investments
ASSETS:
Total assets at fair value	218	314
International government securities | Long-term Investments
ASSETS:
Total assets at fair value	884	800
U.S. government securities | Cash Equivalents
ASSETS:
Total assets at fair value		1
U.S. government securities | Short-term Investments
ASSETS:
Total assets at fair value	241	656
U.S. government securities | Long-term Investments
ASSETS:
Total assets at fair value	246	293
Corporate debt securities | Short-term Investments
ASSETS:
Total assets at fair value	1,514	2,681
Corporate debt securities | Long-term Investments
ASSETS:
Total assets at fair value	3,783	4,401
U.S. government agency securities | Short-term Investments
ASSETS:
Total assets at fair value	1	1
Commercial paper | Cash Equivalents
ASSETS:
Total assets at fair value		2
Commercial paper | Short-term Investments
ASSETS:
Total assets at fair value	4	7
Time deposits and certificates of deposit | Cash Equivalents
ASSETS:
Total assets at fair value	26	25
Time deposits and certificates of deposit | Short-term Investments
ASSETS:
Total assets at fair value	3	1
Marketable equity securities | Long-term Investments
ASSETS:
Total assets at fair value	1,487	1,036
Level 1
ASSETS:
Total assets at fair value	3,243	3,123
Level 1 | Foreign Currency Contracts
ASSETS:
Total assets at fair value	0	0
LIABILITIES:
Total liabilities at fair value	0
Level 1 | Other Long-term Investments [Member]
ASSETS:
Total assets at fair value	0	0
Level 1 | Money market funds | Cash Equivalents
ASSETS:
Total assets at fair value	1,727	2,061
Level 1 | International government securities | Cash Equivalents
ASSETS:
Total assets at fair value		0
Level 1 | International government securities | Short-term Investments
ASSETS:
Total assets at fair value	0	0
Level 1 | International government securities | Long-term Investments
ASSETS:
Total assets at fair value	0	0
Level 1 | U.S. government securities | Cash Equivalents
ASSETS:
Total assets at fair value		0
Level 1 | U.S. government securities | Short-term Investments
ASSETS:
Total assets at fair value	0	0
Level 1 | U.S. government securities | Long-term Investments
ASSETS:
Total assets at fair value	0	0
Level 1 | Corporate debt securities | Short-term Investments
ASSETS:
Total assets at fair value	0	0
Level 1 | Corporate debt securities | Long-term Investments
ASSETS:
Total assets at fair value	0	0
Level 1 | U.S. government agency securities | Short-term Investments
ASSETS:
Total assets at fair value	0	0
Level 1 | Commercial paper | Cash Equivalents
ASSETS:
Total assets at fair value		0
Level 1 | Commercial paper | Short-term Investments
ASSETS:
Total assets at fair value	0	0
Level 1 | Time deposits and certificates of deposit | Cash Equivalents
ASSETS:
Total assets at fair value	26	25
Level 1 | Time deposits and certificates of deposit | Short-term Investments
ASSETS:
Total assets at fair value	3	1
Level 1 | Marketable equity securities | Long-term Investments
ASSETS:
Total assets at fair value	1,487	1,036
Level 2
ASSETS:
Total assets at fair value	8,236	10,358
Level 2 | Foreign Currency Contracts
ASSETS:
Total assets at fair value	1	4
LIABILITIES:
Total liabilities at fair value	2
Level 2 | Other Long-term Investments [Member]
ASSETS:
Total assets at fair value	0	0
Level 2 | Money market funds | Cash Equivalents
ASSETS:
Total assets at fair value	0	0
Level 2 | International government securities | Cash Equivalents
ASSETS:
Total assets at fair value		21
Level 2 | International government securities | Short-term Investments
ASSETS:
Total assets at fair value	218	314
Level 2 | International government securities | Long-term Investments
ASSETS:
Total assets at fair value	884	800
Level 2 | U.S. government securities | Cash Equivalents
ASSETS:
Total assets at fair value		1
Level 2 | U.S. government securities | Short-term Investments
ASSETS:
Total assets at fair value	241	656
Level 2 | U.S. government securities | Long-term Investments
ASSETS:
Total assets at fair value	246	293
Level 2 | Corporate debt securities | Short-term Investments
ASSETS:
Total assets at fair value	1,514	2,681
Level 2 | Corporate debt securities | Long-term Investments
ASSETS:
Total assets at fair value	3,783	4,401
Level 2 | U.S. government agency securities | Short-term Investments
ASSETS:
Total assets at fair value	1	1
Level 2 | Commercial paper | Cash Equivalents
ASSETS:
Total assets at fair value		2
Level 2 | Commercial paper | Short-term Investments
ASSETS:
Total assets at fair value	4	7
Level 2 | Time deposits and certificates of deposit | Cash Equivalents
ASSETS:
Total assets at fair value	0	0
Level 2 | Time deposits and certificates of deposit | Short-term Investments
ASSETS:
Total assets at fair value	0	0
Level 2 | Marketable equity securities | Long-term Investments
ASSETS:
Total assets at fair value	0	0
Level 3
ASSETS:
Total assets at fair value	200	200
Level 3 | Foreign Currency Contracts
ASSETS:
Total assets at fair value	0	0
LIABILITIES:
Total liabilities at fair value	0
Level 3 | Other Long-term Investments [Member]
ASSETS:
Total assets at fair value	200	200
Level 3 | Money market funds | Cash Equivalents
ASSETS:
Total assets at fair value	0	0
Level 3 | International government securities | Cash Equivalents
ASSETS:
Total assets at fair value		0
Level 3 | International government securities | Short-term Investments
ASSETS:
Total assets at fair value	0	0
Level 3 | International government securities | Long-term Investments
ASSETS:
Total assets at fair value	0	0
Level 3 | U.S. government securities | Cash Equivalents
ASSETS:
Total assets at fair value		0
Level 3 | U.S. government securities | Short-term Investments
ASSETS:
Total assets at fair value	0	0
Level 3 | U.S. government securities | Long-term Investments
ASSETS:
Total assets at fair value	0	0
Level 3 | Corporate debt securities | Short-term Investments
ASSETS:
Total assets at fair value	0	0
Level 3 | Corporate debt securities | Long-term Investments
ASSETS:
Total assets at fair value	0	0
Level 3 | U.S. government agency securities | Short-term Investments
ASSETS:
Total assets at fair value	0	0
Level 3 | Commercial paper | Cash Equivalents
ASSETS:
Total assets at fair value		0
Level 3 | Commercial paper | Short-term Investments
ASSETS:
Total assets at fair value	0	0
Level 3 | Time deposits and certificates of deposit | Cash Equivalents
ASSETS:
Total assets at fair value	0	0
Level 3 | Time deposits and certificates of deposit | Short-term Investments
ASSETS:
Total assets at fair value	0	0
Level 3 | Marketable equity securities | Long-term Investments
ASSETS:
Total assets at fair value	0	0
Ctrip.com International, Ltd. | Ctrip convertible debt securities | Long-term Investments
ASSETS:
Total assets at fair value	1,344	1,177
Ctrip.com International, Ltd. | Level 1 | Ctrip convertible debt securities | Long-term Investments
ASSETS:
Total assets at fair value	0	0
Ctrip.com International, Ltd. | Level 2 | Ctrip convertible debt securities | Long-term Investments
ASSETS:
Total assets at fair value	1,344	1,177
Ctrip.com International, Ltd. | Level 3 | Ctrip convertible debt securities | Long-term Investments
ASSETS:
Total assets at fair value	$ 0	$ 0