GENERAL INFORMATION AND OTHER FINANCIAL DATA - EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Net Income/Earnings attributable to common shares	$ 347	$ 441	[1]
Weighted-average common shares outstanding for basic EPS (in shares)	257,932,000	251,131,000	[1]
Dilutive effect of stock options, RSAs and RSUs (in shares)	933,000	1,115,000
Dilutive effect of common stock forward shares (in shares)	625,000	0
Weighted-average common shares outstanding for diluted EPS (in shares)	259,490,000	252,246,000	[1]
Basic earnings per common share (in dollars per share)	$ 1.34	$ 1.76	[1]
Diluted earnings per common share (in dollars per share)	$ 1.33	$ 1.75	[1]
Vested RSUs included in basic WASO	628,000	600,000
Convertible Preferred Stock [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Antidilutive securities excluded from earnings per share	15,592,572
Stock options, RSAs and RSUs [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Antidilutive securities excluded from earnings per share	80,449	6,801
Performance-based RSUs [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Equity awards, granted (in shares)	356,496
Service-based RSUs [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Equity awards, granted (in shares)	195,994
IENova Plans [Member] | RSUs [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Equity awards, granted (in shares)	437,729

[1] As adjusted for the retrospective adoption of ASU 2017-07, which we discuss in Note 2, and a reclassification to conform to current year presentation, which we discuss in Note 1.