SHAREHOLDERS' EQUITY - Stock Repurchase (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	May 31, 2017
Equity [Abstract]
Stock repurchase program, authorized amount				$ 1,500
Repurchase and retirement of common stock (in shares)	9.2	14.9	17.2
Repurchase and retirement of common stock to offset the dilutive impact of the grant of long-term stock awards (in shares)	0.9	1.1	0.7
Remaining authorized repurchase amount	$ 1,300
Repurchase and retirement of common stock	$ 331	$ 459	$ 456