FAIR VALUE MEASUREMENTS Fair Value (Details) - Recurring basis - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
ASSETS:
Total assets at fair value	$ 10,751	$ 13,681
Level 1
ASSETS:
Total assets at fair value	7,556	3,123
Level 2
ASSETS:
Total assets at fair value	2,945	10,358
Level 3
ASSETS:
Total assets at fair value	250	200
Not designated as hedging instrument | Foreign exchange derivatives
ASSETS:
Total assets at fair value	12	4
LIABILITIES:
Fair value of derivative liabilities	5
Not designated as hedging instrument | Foreign exchange derivatives | Level 1
ASSETS:
Total assets at fair value	0	0
LIABILITIES:
Fair value of derivative liabilities	0
Not designated as hedging instrument | Foreign exchange derivatives | Level 2
ASSETS:
Total assets at fair value	12	4
LIABILITIES:
Fair value of derivative liabilities	5	0
Not designated as hedging instrument | Foreign exchange derivatives | Level 3
ASSETS:
Total assets at fair value	0	0
LIABILITIES:
Fair value of derivative liabilities	0
Short-term investments in marketable securities | International government securities
ASSETS:
Total assets at fair value	109	314
Short-term investments in marketable securities | U.S. government securities
ASSETS:
Total assets at fair value	138	656
Short-term investments in marketable securities | Corporate debt securities
ASSETS:
Total assets at fair value	751	2,681
Short-term investments in marketable securities | Commercial paper
ASSETS:
Total assets at fair value		7
Short-term investments in marketable securities | Time deposits and certificates of deposit
ASSETS:
Total assets at fair value		1
Short-term investments in marketable securities | U.S. government agency securities
ASSETS:
Total assets at fair value		1
Short-term investments in marketable securities | Level 1 | International government securities
ASSETS:
Total assets at fair value	0	0
Short-term investments in marketable securities | Level 1 | U.S. government securities
ASSETS:
Total assets at fair value	0	0
Short-term investments in marketable securities | Level 1 | Corporate debt securities
ASSETS:
Total assets at fair value	0	0
Short-term investments in marketable securities | Level 1 | Commercial paper
ASSETS:
Total assets at fair value		0
Short-term investments in marketable securities | Level 1 | Time deposits and certificates of deposit
ASSETS:
Total assets at fair value		1
Short-term investments in marketable securities | Level 1 | U.S. government agency securities
ASSETS:
Total assets at fair value		0
Short-term investments in marketable securities | Level 2 | International government securities
ASSETS:
Total assets at fair value	109	314
Short-term investments in marketable securities | Level 2 | U.S. government securities
ASSETS:
Total assets at fair value	138	656
Short-term investments in marketable securities | Level 2 | Corporate debt securities
ASSETS:
Total assets at fair value	751	2,681
Short-term investments in marketable securities | Level 2 | Commercial paper
ASSETS:
Total assets at fair value		7
Short-term investments in marketable securities | Level 2 | Time deposits and certificates of deposit
ASSETS:
Total assets at fair value		0
Short-term investments in marketable securities | Level 2 | U.S. government agency securities
ASSETS:
Total assets at fair value		1
Short-term investments in marketable securities | Level 3 | International government securities
ASSETS:
Total assets at fair value	0	0
Short-term investments in marketable securities | Level 3 | U.S. government securities
ASSETS:
Total assets at fair value	0	0
Short-term investments in marketable securities | Level 3 | Corporate debt securities
ASSETS:
Total assets at fair value	0	0
Short-term investments in marketable securities | Level 3 | Commercial paper
ASSETS:
Total assets at fair value		0
Short-term investments in marketable securities | Level 3 | Time deposits and certificates of deposit
ASSETS:
Total assets at fair value		0
Short-term investments in marketable securities | Level 3 | U.S. government agency securities
ASSETS:
Total assets at fair value		0
Long-term investments
ASSETS:
Total assets at fair value	250	200
Long-term investments | International government securities
ASSETS:
Total assets at fair value	68	800
Long-term investments | U.S. government securities
ASSETS:
Total assets at fair value	135	293
Long-term investments | Corporate debt securities
ASSETS:
Total assets at fair value	963	4,401
Long-term investments | Equity securities
ASSETS:
Total assets at fair value	1,793	1,036
Long-term investments | Level 1
ASSETS:
Total assets at fair value	0	0
Long-term investments | Level 1 | International 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 | Corporate debt securities
ASSETS:
Total assets at fair value	0	0
Long-term investments | Level 1 | Equity securities
ASSETS:
Total assets at fair value	1,793	1,036
Long-term investments | Level 2
ASSETS:
Total assets at fair value	0	0
Long-term investments | Level 2 | International government securities
ASSETS:
Total assets at fair value	68	800
Long-term investments | Level 2 | U.S. government securities
ASSETS:
Total assets at fair value	135	293
Long-term investments | Level 2 | Corporate debt securities
ASSETS:
Total assets at fair value	963	4,401
Long-term investments | Level 2 | Equity securities
ASSETS:
Total assets at fair value	0	0
Long-term investments | Level 3
ASSETS:
Total assets at fair value	250	200
Long-term investments | Level 3 | International government securities
ASSETS:
Total assets at fair value	0	0
Long-term investments | Level 3 | U.S. government securities
ASSETS:
Total assets at fair value	0	0
Long-term investments | Level 3 | Corporate debt securities
ASSETS:
Total assets at fair value	0	0
Long-term investments | Level 3 | Equity securities
ASSETS:
Total assets at fair value	0	0
Long-term investments | Trip.com Group | Trip.com Group convertible debt securities
ASSETS:
Total assets at fair value	767	1,177
Long-term investments | Trip.com Group | Level 1 | Trip.com Group convertible debt securities
ASSETS:
Total assets at fair value	0	0
Long-term investments | Trip.com Group | Level 2 | Trip.com Group convertible debt securities
ASSETS:
Total assets at fair value	767	1,177
Long-term investments | Trip.com Group | Level 3 | Trip.com Group convertible debt securities
ASSETS:
Total assets at fair value	0	0
Cash equivalents | Money market funds
ASSETS:
Total assets at fair value	5,734	2,061
Cash equivalents | International government securities
ASSETS:
Total assets at fair value		21
Cash equivalents | U.S. government securities
ASSETS:
Total assets at fair value		1
Cash equivalents | Corporate debt securities
ASSETS:
Total assets at fair value	2
Cash equivalents | Commercial paper
ASSETS:
Total assets at fair value		2
Cash equivalents | Time deposits and certificates of deposit
ASSETS:
Total assets at fair value	29	25
Cash equivalents | Level 1 | Money market funds
ASSETS:
Total assets at fair value	5,734	2,061
Cash equivalents | Level 1 | International government securities
ASSETS:
Total assets at fair value		0
Cash equivalents | Level 1 | U.S. government securities
ASSETS:
Total assets at fair value		0
Cash equivalents | Level 1 | Corporate debt securities
ASSETS:
Total assets at fair value	0
Cash equivalents | Level 1 | Commercial paper
ASSETS:
Total assets at fair value		0
Cash equivalents | Level 1 | Time deposits and certificates of deposit
ASSETS:
Total assets at fair value	29	25
Cash equivalents | Level 2 | Money market funds
ASSETS:
Total assets at fair value	0	0
Cash equivalents | Level 2 | International government securities
ASSETS:
Total assets at fair value		21
Cash equivalents | Level 2 | U.S. government securities
ASSETS:
Total assets at fair value		1
Cash equivalents | Level 2 | Corporate debt securities
ASSETS:
Total assets at fair value	2
Cash equivalents | Level 2 | Commercial paper
ASSETS:
Total assets at fair value		2
Cash equivalents | Level 2 | Time deposits and certificates of deposit
ASSETS:
Total assets at fair value	0	0
Cash equivalents | Level 3 | Money market funds
ASSETS:
Total assets at fair value	0	0
Cash equivalents | Level 3 | International government securities
ASSETS:
Total assets at fair value		0
Cash equivalents | Level 3 | U.S. government securities
ASSETS:
Total assets at fair value		0
Cash equivalents | Level 3 | Corporate debt securities
ASSETS:
Total assets at fair value	0
Cash equivalents | Level 3 | Commercial paper
ASSETS:
Total assets at fair value		0
Cash equivalents | Level 3 | Time deposits and certificates of deposit
ASSETS:
Total assets at fair value	$ 0	$ 0