CONSOLIDATED STATEMENTS OF INCOME (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Utility revenues	$ 3,294.5	$ 3,368.5	$ 3,495.8
Nonregulated revenues	1,414.2	1,834.7	4,004.0
Total revenues	4,708.7	5,203.2	7,499.8
Utility cost of fuel, natural gas, and purchased power	1,635.3	1,685.5	1,919.8
Nonregulated cost of sales	1,281.6	1,619.8	3,701.3
Operating and maintenance expense	1,028.2	1,045.6	1,098.4
Impairment losses on property, plant, and equipment	4.6	43.2	0.7
Restructuring expense	2.0	7.9	43.5
Net (gain) loss on Integrys Energy Services' dispositions related to strategy change	(0.3)	14.1	28.9
Goodwill impairment loss			291.1
Depreciation and amortization expense	250.1	265.8	230.6
Taxes other than income taxes	98.4	93.2	96.3
Operating income	408.8	428.1	89.2
Miscellaneous income	84.8	91.5	89.0
Interest expense	(128.8)	(147.9)	(164.8)
Other expense	(44.0)	(56.4)	(75.8)
Income before taxes	364.8	371.7	13.4
Provision for income taxes	133.9	148.2	83.7
Net income (loss) from continuing operations	230.9	223.5	(70.3)
Discontinued operations, net of tax	(0.4)	0.2	2.8
Net income (loss)	230.5	223.7	(67.5)
Preferred stock dividends of subsidiary	(3.1)	(3.1)	(3.1)
Noncontrolling interest in subsidiaries		0.3	1.0
Net income (loss) attributed to common shareholders	$ 227.4	$ 220.9	$ (69.6)
Average shares of common stock
Basic (in shares)	78.6	77.5	76.8
Diluted (in shares)	79.1	78.0	76.8
Earnings (loss) per common share (basic)
Net income (loss) from continuing operations (in dollars per share)	$ 2.90	$ 2.85	$ (0.95)
Discontinued operations, net of tax (in dollars per share)	$ (0.01)		$ 0.04
Earnings (loss) per common share (basic) (in dollars per share)	$ 2.89	$ 2.85	$ (0.91)
Earnings (loss) per common share (diluted)
Net income (loss) from continuing operations (in dollars per share)	$ 2.88	$ 2.83	$ (0.95)
Discontinued operations, net of tax (in dollars per share)	$ (0.01)		$ 0.04
Earnings (loss) per common share (diluted) (in dollars per share)	$ 2.87	$ 2.83	$ (0.91)
Dividends per common share declared (in dollars per share)	$ 2.72	$ 2.72	$ 2.72