Summary Of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Public Utility Property Plant And Equipment [Line Items]
Regulatory liabilities	915.9	899.1
Percentage of AFUDC for biomass project	100.00%
PWGS 1 [Member]
Public Utility Property Plant And Equipment [Line Items]
Depreciation over an estimated useful life	10 to 45 years
PWGS 2 [Member]
Public Utility Property Plant And Equipment [Line Items]
Depreciation over an estimated useful life	10 to 45 years
OC 1 [Member]
Public Utility Property Plant And Equipment [Line Items]
Depreciation over an estimated useful life	10 to 55 years
OC 2 [Member]
Public Utility Property Plant And Equipment [Line Items]
Depreciation over an estimated useful life	10 to 55 years
Wisconsin Electric [Member]
Public Utility Property Plant And Equipment [Line Items]
Interest rate on accrued AFUDC	8.83%	8.83%	9.09%
Percentage of specific Wisconsin Electric CWIP project which accrue AFUDC	100.00%	100.00%	100.00%
Percentage of all Wisconsin Electric utility CWIP projects except specific project which accrue AFUDC	50.00%	50.00%	50.00%
Wisconsin Gas [Member]
Public Utility Property Plant And Equipment [Line Items]
Interest rate on accrued AFUDC	9.05%	9.05%	10.80%
Percentage of Wisconsin Gas CWIP projects which accrued AFUDC	50.00%	50.00%	50.00%
Asset Retirement Obligation Costs [Member]
Public Utility Property Plant And Equipment [Line Items]
Regulatory liabilities	728.2	723.9