Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator:
Net income	$ 77.6	$ 191.6	$ 84.6	$ 240.8
Preferred stock dividends	2.6	2.6	5.2	5.2
Net income applicable to common shareowners - basic and diluted	$ 75.0	$ 189.0	$ 79.4	$ 235.6
Denominator:
Weighted average common shares outstanding - basic	209.8	209.7	209.9	209.4
Stock-based compensation arrangements	0.6	0.4	0.5	0.7
Conversion of preferred shares	0.0	4.5
Weighted average common shares outstanding - diluted	210.4	214.6	210.4	210.1
Basic earnings per common share from continuing operations	$ 0.36	$ 0.85	$ 0.38	$ 0.84
Basic earnings per common share from discontinued operations	0.00	0.05	0.00	0.29
Basic earnings per common share	0.36	0.90	0.38	1.13
Diluted earnings per common share from continuing operations	0.36	0.84	0.38	0.84
Diluted earnings per common share from discontinued operations	0.00	0.05	0.00	0.28
Diluted earnings per common share	$ 0.36	$ 0.89	$ 0.38	$ 1.12
Continuing Operations [Member]
Numerator:
Net income	$ 77.6	$ 180.7	$ 84.6	$ 181.0
Preferred stock dividends	2.6	2.6	5.2	5.2
Net income applicable to common shareowners - basic and diluted	$ 75.0	$ 178.1	$ 79.4	$ 175.8
Denominator:
Weighted average common shares outstanding - basic	209.8	209.7	209.9	209.4
Stock-based compensation arrangements	0.6	0.4	0.5	0.7
Conversion of preferred shares	0.0	4.5
Weighted average common shares outstanding - diluted	210.4	214.6	210.4	210.1
Discontinued Operations [Member]
Numerator:
Net income	$ 0.0	$ 10.9	$ 0.0	$ 59.8
Preferred stock dividends	0.0	0.0	0.0	0.0
Net income applicable to common shareowners - basic and diluted	$ 0.0	$ 10.9	$ 0.0	$ 59.8
Denominator:
Weighted average common shares outstanding - basic	209.8	209.7	209.9	209.4
Stock-based compensation arrangements	0.6	0.4	0.5	0.7
Conversion of preferred shares	0.0	4.5
Weighted average common shares outstanding - diluted	210.4	214.6	210.4	210.1
Stock Compensation Plan [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2.2	3.4	2.6	3.7
Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	4.5		4.5	4.5

The amount of net income or loss for the period in instances when the basic and diluted net income or loss available to common stockholders are the same amount and reported as a single line item on the face of the financial statements. Basic net income (loss) available to common stockholders is net income or loss after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period). Diluted net income (loss) available to common stockholders is net income or loss plus adjustments resulting from the assumption that dilutive convertible securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions.

No definition available.