EARNINGS PER COMMON SHARE - Reconciliations of the Numerators and Denominators Used in the Computations of Basic and Diluted Earnings per Common Share (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator (basic and diluted):
Income from continuing operations	$ 533	$ 491	$ 357
Less: Allocation to unvested restricted stock awards	5	6	5
Income from continuing operations attributable to common shareholders	528	485	352
(Loss) income from discontinued operations, net	0	0	(2)
Less: Allocation to unvested restricted stock awards	0	0	0
(Loss) income from discontinued operations attributable to common shareholders	0	0	(2)
Net income available to common shareholders	$ 528	$ 485	$ 350
Denominator:
Basic common shares (based upon weighted average) (in shares)	314	326	338
Add: Stock option dilution (in shares)	4	4	3
Diluted common shares (in shares)	318	330	341