Short-Term Debt (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Short-Term Debt (Textuals) [Abstract]
Undrawn lines under bank back-up credit facilities	$ 1,200,000,000
Short-term debt outstanding supported by the available lines of credit	669,900,000
Wisconsin Energy Corporation [Member]
Short-Term Debt (Textuals) [Abstract]
Minimum total funded debt to capitalization ratio	70.00%
Wisconsin Electric [Member]
Short-Term Debt (Textuals) [Abstract]
Minimum total funded debt to capitalization ratio	65.00%
Wisconsin Gas [Member]
Short-Term Debt (Textuals) [Abstract]
Minimum total funded debt to capitalization ratio	65.00%
Commercial Paper [Member]
Short-term notes payable balances and their corresponding weighted-average interest rates
Commercial paper, balance	669,900,000	657,900,000
Commercial paper, weighted-average interest rate	0.27%	0.30%
Commercial paper [Abstract]
Maximum Short-Term Debt Outstanding	717,300,000	821,000,000
Average Short-Term Debt Outstanding	$ 505,100,000	$ 528,700,000
Weighted-Average Interest Rate	0.25%	0.32%