Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011		Dec. 31, 2011
Financial information of reportable operating segments
Operating Revenues	$ 1,191.2	[1]	$ 1,328.7	[1]
Other operation and maintenance	286.3		313.5
Depreciation and Amortization	87.6		81.3
Operating Income (Loss)	295.7		295.6
Equity in Earnings of Unconsolidated Affiliates	15.6		15.4
Interest Expense, net	58.9		63.4
Income Tax Expense (Benefit)	96.3		89.3
Net Income (Loss)	172.1		170.9
Capital Expenditures	142.3		135.5
Total Assets	13,821.3	[2]	13,188.6	[2]	13,862.1
Segment Information (Textuals)
Elimination included in Total Assets	2,355.9		2,437.8
Reportable Operating Segments Energy Utility [Member]
Financial information of reportable operating segments
Operating Revenues	1,178.4	[1]	1,316.5	[1]
Other operation and maintenance	376.4		400.9
Depreciation and Amortization	70.7		63.4
Operating Income (Loss)	208.6		213.0
Equity in Earnings of Unconsolidated Affiliates	15.6		15.5
Interest Expense, net	29.2		28.1
Income Tax Expense (Benefit)	74.0		71.3
Net Income (Loss)	136.2		141.0
Capital Expenditures	137.6		127.2
Total Assets	13,429.0	[2]	12,632.8	[2]
Reportable Operating Segments Energy Non Utility [Member]
Financial information of reportable operating segments
Operating Revenues	107.3	[1]	103.2	[1]
Other operation and maintenance	2.1		1.5
Depreciation and Amortization	16.8		17.7
Operating Income (Loss)	88.4		84.0
Equity in Earnings of Unconsolidated Affiliates	0		0
Interest Expense, net	16.8		15.9
Income Tax Expense (Benefit)	28.8		27.7
Net Income (Loss)	43.0		40.5
Capital Expenditures	1.9		8.2
Total Assets	2,932.6	[2]	2,975.9	[2]
Corporate and Other [Member]
Financial information of reportable operating segments
Operating Revenues	0.3	[1],[3]	0.2	[1],[3]
Other operation and maintenance	1.3	[3]	1.1	[3]
Depreciation and Amortization	0.1	[3]	0.2	[3]
Operating Income (Loss)	(1.3)	[3]	(1.4)	[3]
Equity in Earnings of Unconsolidated Affiliates	0	[3]	(0.1)	[3]
Interest Expense, net	13.1	[3]	19.5	[3]
Income Tax Expense (Benefit)	(6.5)	[3]	(9.7)	[3]
Net Income (Loss)	172.6	[3]	170.8	[3]
Capital Expenditures	2.8	[3]	0.1	[3]
Total Assets	4,771.9	[2],[3]	4,913.6	[2],[3]
Eliminations and Reconciling Items [Member]
Financial information of reportable operating segments
Operating Revenues	(94.8)	[1]	(91.2)	[1]
Other operation and maintenance	(93.5)		(90.0)
Depreciation and Amortization	0		0
Operating Income (Loss)	0		0
Equity in Earnings of Unconsolidated Affiliates	0		0
Interest Expense, net	(0.2)		(0.1)
Income Tax Expense (Benefit)	0		0
Net Income (Loss)	(179.7)		(181.4)
Capital Expenditures	0		0
Total Assets	$ (7,312.2)	[2]	$ (7,333.7)	[2]

[1] An elimination for intersegment revenues is included in Operating Revenues. This elimination is primarily between We Power and Wisconsin Electric.

[2] An elimination of $2,355.9 million and $2,437.8 million is included in Total Assets as of March 31, 2012 and 2011, respectively, for all PTF-related activity between We Power and Wisconsin Electric.

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