OTHER FINANCIAL DATA - EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016		Jun. 30, 2017	Jun. 30, 2016
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Earnings attributable to common shares	$ 259	$ 16	[1]	$ 700	$ 369	[1]
Weighted-average common shares outstanding for basic EPS (in shares)	251,447,000	250,096,000	[1]	251,290,000	249,915,000	[1]
Vested RSUs included in basic WASO	608	568		604	562
Dilutive effect of stock options, restricted stock awards and restricted stock units (in shares)	1,375,000	1,940,000		1,319,000	1,860,000
Weighted-average common shares outstanding for diluted EPS (in shares)	252,822,000	252,036,000	[1]	252,609,000	251,775,000	[1]
Basic earnings per common share (in dollars per share)	$ 1.03	$ 0.06	[1]	$ 2.79	$ 1.48	[1]
Diluted earnings per common share (in dollars per share)	$ 1.03	$ 0.06	[1]	$ 2.77	$ 1.47	[1]
Antidilutive securities excluded from earnings per share	3,010	1,010		3,010	2,408
Performance-based RSUs [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Equity awards, granted (in shares)	424,760
Service-based RSUs [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Equity awards, granted (in shares)	93,619
IENova Plans [Member] | RSUs [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Equity awards, granted (in shares)	1,034,086

[1] As adjusted for the adoption of ASU 2016-09 as of January 1, 2016.