Segment Information (Details) (USD $) In Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010		Dec. 31, 2010
Financial information of reportable operating segments
Operating Revenues	$ 1,052.8	[1]	$ 973.2	[1]	$ 3,373.2	[1]	$ 3,112.7	[1]
Segment Reporting Information, Depreciation, Depletion, and Amortization Expense	82.6		77.4		246.2		228.6
Operating Income (Loss)	224.3		203.0		694.3		594.7
Equity in Earnings (Loss) of Unconsolidated Affiliates	15.6		15.1		46.1		45.5
Interest Expense, net	56.8		52.5		177.6		154.9
Income Tax Expense (Benefit)	69.6		63.0		207.5		182.0
Income (Loss) from Discontinued Operations, Net of Tax	0		(0.1)		11.5		1.8
Net Income (Loss)	129.8		112.2		410.2		330.6
Capital Expenditures	265.1		166.5		612.2		545.6
Total Assets	13,249.5	[2]	12,718.5	[2]	13,249.5	[2]	12,718.5	[2]	13,059.8
Segment Information (Textuals)
Segment Reporting Information, Intersegment Revenue	97.2		75.0		286.1		211.2
Elimination included in Total Assets	2,392.0		1,803.3		2,392.0		1,803.3
Reportable Operating Segments Energy Utility [Member]
Financial information of reportable operating segments
Operating Revenues	1,036.7	[1]	960.5	[1]	3,331.1	[1]	3,083.9	[1]
Segment Reporting Information, Depreciation, Depletion, and Amortization Expense	64.1		63.2		191.4		188.4
Operating Income (Loss)	135.6		134.2		436.7		410.1
Equity in Earnings (Loss) of Unconsolidated Affiliates	15.7		15.2		46.4		45.5
Interest Expense, net	26.8		29.2		82.1		88.9
Income Tax Expense (Benefit)	45.5		44.6		145.9		138.9
Income (Loss) from Discontinued Operations, Net of Tax	0		0		0		0.7
Net Income (Loss)	95.0		84.7		297.1		252.9
Capital Expenditures	252.1		149.2		583.1		445.1
Total Assets	12,847.8	[2]	11,700.2	[2]	12,847.8	[2]	11,700.2	[2]
Reportable Operating Segments Energy Non Utility [Member]
Financial information of reportable operating segments
Operating Revenues	113.0	[1]	87.4	[1]	327.5	[1]	239.5	[1]
Segment Reporting Information, Depreciation, Depletion, and Amortization Expense	18.3		13.9		54.3		39.5
Operating Income (Loss)	89.8		69.0		261.7		188.0
Equity in Earnings (Loss) of Unconsolidated Affiliates	0		0		0		0
Interest Expense, net	16.9		11.0		49.8		28.9
Income Tax Expense (Benefit)	28.4		22.2		84.2		62.7
Income (Loss) from Discontinued Operations, Net of Tax	0		0		0		0
Net Income (Loss)	44.6		36.3		127.9		96.8
Capital Expenditures	7.3		16.6		22.2		99.0
Total Assets	2,958.4	[2]	2,965.3	[2]	2,958.4	[2]	2,965.3	[2]
Corporate and Other and Reconciling Items [Member]
Financial information of reportable operating segments
Operating Revenues	(96.9)	[1],[3]	(74.7)	[1],[3]	(285.4)	[1],[3]	(210.7)	[1],[3]
Segment Reporting Information, Depreciation, Depletion, and Amortization Expense	0.2	[3]	0.3	[3]	0.5	[3]	0.7	[3]
Operating Income (Loss)	(1.1)	[3]	(0.2)	[3]	(4.1)	[3]	(3.4)	[3]
Equity in Earnings (Loss) of Unconsolidated Affiliates	(0.1)	[3]	(0.1)	[3]	(0.3)	[3]	0	[3]
Interest Expense, net	13.1	[3]	12.3	[3]	45.7	[3]	37.1	[3]
Income Tax Expense (Benefit)	(4.3)	[3]	(3.8)	[3]	(22.6)	[3]	(19.6)	[3]
Income (Loss) from Discontinued Operations, Net of Tax	0	[3]	(0.1)	[3]	11.5	[3]	1.1	[3]
Net Income (Loss)	(9.8)	[3]	(8.8)	[3]	(14.8)	[3]	(19.1)	[3]
Capital Expenditures	5.7	[3]	0.7	[3]	6.9	[3]	1.5	[3]
Total Assets	$ (2,556.7)	[2],[3]	$ (1,947.0)	[2],[3]	$ (2,556.7)	[2],[3]	$ (1,947.0)	[2],[3]

[1] An elimination for intersegment revenues of $97.2 million and $75.0 million for the three months ended September 30, 2011 and 2010, respectively, and $286.1 million and $211.2 million for the nine months ended September 30, 2011 and 2010, respectively, is included in Operating Revenues. This elimination is primarily between We Power and Wisconsin Electric.

[2] An elimination of $2,392.0 million and $1,803.3 million is included in Total Assets as of September 30, 2011 and 2010, respectively, for PTF-related activity between We Power and Wisconsin Electric.

[3] Other includes all other non-utility activities, primarily non-utility real estate investment and development by Wispark LLC, as well as interest on corporate debt.