SHAREHOLDERS' EQUITY - Stock Repurchase (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	May 31, 2017
Equity [Abstract]
Stock repurchase program, authorized amount				$ 1,500
Repurchase and retirement of common stock (in shares)	18.6	9.2	14.9
Repurchase and retirement of common stock to offset the dilutive impact of the grant of long-term stock awards (in shares)	0.7	0.9	1.1
Remaining authorized repurchase amount	$ 636
Repurchase and retirement of common stock	$ 654	$ 331	$ 459