COMMON EQUITY - EARNINGS PER SHARE (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Numerator:
Net income (loss) from continuing operations	$ 8.1	$ (3.9)	$ 161.3	$ 178.3
Discontinued operations, net of tax	(0.1)	(0.8)	(0.2)	5.3
Preferred stock dividends of subsidiary	(0.8)	(0.8)	(1.6)	(1.6)
Noncontrolling interest in subsidiaries	0	0.1	0.1	0.1
Net income (loss) attributed to common shareholders	$ 7.2	$ (5.4)	$ 159.6	$ 182.1
Denominator:
Average shares of common stock — basic	80.2	79.4	80.2	79.0
Effect of dilutive securities
Stock-based compensation (in shares)	0.3	0	0.3	0.3
Deferred compensation (in shares)	0	0	0	0.4
Average shares of common stock - diluted	80.5	79.4	80.5	79.7
Earnings (loss) per common share
Basic (in dollars per share)	$ 0.09	$ (0.07)	$ 1.99	$ 2.31
Diluted (in dollars per share)	$ 0.09	$ (0.07)	$ 1.98	$ 2.29
Stock-based compensation
Disclosure of antidilutive shares
Weighted-average outstanding securities that had an anti-dilutive effect	0	0	0.4	0.2
Deferred compensation
Disclosure of antidilutive shares
Weighted-average outstanding securities that had an anti-dilutive effect	0.3	0	0.3	0