COMMON EQUITY - EARNINGS PER SHARE (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Numerator:
Net income from continuing operations	$ 131.2	$ 140.2
Discontinued operations, net of tax	(0.9)	12.9
Preferred stock dividends of subsidiary	(0.8)	(0.8)
Noncontrolling interest in subsidiaries	0	0.1
Net income attributed to common shareholders	129.5	152.4
Net income attributed to common shareholders — diluted	128.9	152.4
Denominator:
Average shares of common stock — basic	80.2	80.2
Average shares of common stock - diluted	80.8	80.5
Earnings per common share
Basic (in dollars per share)	$ 1.61	$ 1.90
Diluted (in dollars per share)	$ 1.60	$ 1.89
Stock-based compensation
Denominator:
Effect of dilutive securities	0.4	0.3
Deferred compensation
Numerator:
Effect of dilutive securities	$ (0.6)	$ 0
Denominator:
Effect of dilutive securities	0.2	0