CONDENSED CONSOLIDATED STATEMENTS OF INCOME (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
CONDENSED CONSOLIDATED STATEMENTS OF INCOME
Utility revenues	$ 1,123.8	$ 971.0
Nonregulated revenues	554.4	276.9
Total revenues	1,678.2	1,247.9
Utility cost of fuel, natural gas, and purchased power	565.1	472.3
Nonregulated cost of sales	436.8	273.7
Operating and maintenance expense	295.1	259.3
Depreciation and amortization expense	60.9	62.1
Taxes other than income taxes	27.2	27.4
Operating income	293.1	153.1
Earnings from equity method investments	22.3	21.1
Miscellaneous income	5.7	2.4
Interest expense	(29.3)	(30.4)
Other expense	(1.3)	(6.9)
Income before taxes	291.8	146.2
Provision for income taxes	109.6	47.4
Net income from continuing operations	182.2	98.8
Discontinued operations, net of tax	6.1	0.9
Net income	188.3	99.7
Preferred stock dividends of subsidiary	(0.8)	(0.8)
Net income attributed to common shareholders	$ 187.5	$ 98.9
Average shares of common stock
Basic (in shares)	78.7	78.6
Diluted (in shares)	79.3	79.2
Earnings per common share (basic)
Net income from continuing operations (in dollars per share)	$ 2.30	$ 1.25
Discontinued operations, net of tax (in dollars per share)	$ 0.08	$ 0.01
Earnings per common share (basic) (in dollars per share)	$ 2.38	$ 1.26
Earnings per common share (diluted)
Net income from continuing operations (in dollars per share)	$ 2.29	$ 1.24
Discontinued operations, net of tax (in dollars per share)	$ 0.08	$ 0.01
Earnings per common share (diluted) (in dollars per share)	$ 2.37	$ 1.25
Dividends per common share declared (in dollars per share)	$ 0.68	$ 0.68