Common Equity (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended				12 Months Ended
	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common Stock, Shares Authorized					325,000,000	325,000,000
Recorded pre-tax share-based compensation expense and related tax benefit for share-based awards made to employees and directors
Share-based compensation expense					$ 19.0	$ 22.0	$ 28.5
Common Equity (Textuals)
Actual tax benefit realized for the tax deductions from option exercises/settlement					17.8	0	14.3
Common Stock, Shares, Outstanding					225,962,959	229,039,456
Related Tax Benefit					7.6	8.8	11.4
Maximum [Member]
Common Equity (Textuals)
Requirement to maintain common equity ratio by Wisconsin Electric					53.50%
Requirement to maintain common equity ratio by Wisconsin Gas					50.00%
Minimum [Member]
Common Equity (Textuals)
Requirement to maintain common equity ratio by Wisconsin Electric					48.50%
Requirement to maintain common equity ratio by Wisconsin Gas					45.00%
Performance Units [Member]
Recorded pre-tax share-based compensation expense and related tax benefit for share-based awards made to employees and directors
Share-based compensation expense					12.7	16.3	24.1
Related Tax Benefit					5.3	7.0	9.7
Restricted stock activity
Granted, Number of Shares	233,735	239,120	346,570	435,690
Common Equity (Textuals)
Unrecognized total compensation costs related share based compensation					10.8
Months, on a weighted-average basis, expected for recognizing total compensation costs related to non-vested stock options					20 months
Intrinsic Value					14.8	19.3	26.7
Stock Options [Member]
Recorded pre-tax share-based compensation expense and related tax benefit for share-based awards made to employees and directors
Share-based compensation expense					3.9	2.7	2.6
Non-Vested Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value						$ 3.31
Common Equity (Textuals)
Unrecognized total compensation costs related share based compensation					2.0
Months, on a weighted-average basis, expected for recognizing total compensation costs related to non-vested stock options					21 months
Restricted Stock [Member]
Recorded pre-tax share-based compensation expense and related tax benefit for share-based awards made to employees and directors
Share-based compensation expense					2.4	3.0	1.8
Related Tax Benefit					1.3	0	0.8
Restricted stock activity
Outstanding	150,698	188,222			188,222
Granted, Number of Shares	71,504				74,290
Granted, Weighted-Average Market Price					$ 37.65
Released, Number of Shares					(97,973)
Released, Weighted-Average Market Price					$ 26.65
Forfeited, Number of Shares					(13,841)
Forfeited, Weighted-Average Market Price					$ 33.35
Outstanding					150,698	188,222
Common Equity (Textuals)
Unrecognized total compensation costs related share based compensation					2.6
Months, on a weighted-average basis, expected for recognizing total compensation costs related to non-vested stock options					20 months
Restricted stock vesting period in years	3 years
Intrinsic Value					$ 4.0	$ 3.5	$ 2.5