COMMON EQUITY - EARNINGS PER SHARE (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Numerator:
Net income from continuing operations	$ 153.2	$ 182.2
Discontinued operations, net of tax	(0.1)	6.1
Preferred stock dividends of subsidiary	(0.8)	(0.8)
Noncontrolling interest in subsidiaries	0.1	0
Net income attributed to common shareholders	$ 152.4	$ 187.5
Denominator:
Average shares of common stock - basic	80.2	78.7
Effect of dilutive securities
Stock-based compensation (in shares)	0.3	0.4
Deferred compensation (in shares)	0	0.2
Average shares of common stock - diluted	80.5	79.3
Earnings per common share
Basic (in dollars per share)	$ 1.90	$ 2.38
Diluted (in dollars per share)	$ 1.89	$ 2.37
Stock-based compensation
Disclosure of antidilutive shares
Weighted-average outstanding securities that had an anti-dilutive effect	0.7	0.2
Deferred compensation
Disclosure of antidilutive shares
Weighted-average outstanding securities that had an anti-dilutive effect	0.3	0