Consolidated Statements of Capitalization (Parenthetical) (USD $)																																																			12 Months Ended
	Dec. 31, 2012 Debentures (unsecured), 4.50% due 2013 [Member]	Dec. 31, 2011 Debentures (unsecured), 4.50% due 2013 [Member]	Dec. 31, 2012 Debentures (unsecured), 6.60% due 2013 [Member]	Dec. 31, 2011 Debentures (unsecured), 6.60% due 2013 [Member]	Dec. 31, 2012 Debentures (unsecured), 6.00% due 2014 [Member]	Dec. 31, 2011 Debentures (unsecured), 6.00% due 2014 [Member]	Dec. 31, 2012 Debentures (unsecured), 5.20% due 2015 [Member]	Dec. 31, 2011 Debentures (unsecured), 5.20% due 2015 [Member]	Dec. 31, 2012 Debentures (unsecured), 6.25% due 2015 [Member]	Dec. 31, 2011 Debentures (unsecured), 6.25% due 2015 [Member]	Dec. 31, 2012 Debentures (unsecured), 4.25% due 2019 [Member]	Dec. 31, 2011 Debentures (unsecured), 4.25% due 2019 [Member]	Dec. 31, 2012 Debentures (unsecured) 2.95% due 2021 [Member]	Dec. 31, 2011 Debentures (unsecured) 2.95% due 2021 [Member]	Dec. 31, 2012 Debentures (unsecured), 6-1/2% due 2028 [Member]	Dec. 31, 2011 Debentures (unsecured), 6-1/2% due 2028 [Member]	Dec. 31, 2012 Debentures (unsecured), 5.625% due 2033 [Member]	Dec. 31, 2011 Debentures (unsecured), 5.625% due 2033 [Member]	Dec. 31, 2012 Debentures (unsecured), 5.90% due 2035 [Member]	Dec. 31, 2011 Debentures (unsecured), 5.90% due 2035 [Member]	Dec. 31, 2012 Debentures (unsecured), 5.70% due 2036 [Member]	Dec. 31, 2011 Debentures (unsecured), 5.70% due 2036 [Member]	Dec. 31, 2012 Debentures (unsecured), 3.65% due 2042 [Member]	Dec. 31, 2011 Debentures (unsecured), 3.65% due 2042 [Member]	Dec. 31, 2012 Debentures (unsecured), 6-7/8% due 2095 [Member]	Dec. 31, 2011 Debentures (unsecured), 6-7/8% due 2095 [Member]	Dec. 31, 2012 Notes (secured, nonrecourse), 4.81% effective rate due 2030 [Member]	Dec. 31, 2011 Notes (secured, nonrecourse), 4.81% effective rate due 2030 [Member]	Dec. 31, 2012 Notes (secured, nonrecourse), 4.91% due 2012-2030 [Member]	Dec. 31, 2011 Notes (secured, nonrecourse), 4.91% due 2012-2030 [Member]	Dec. 31, 2012 Notes (secured, nonrecourse), 4.673% due 2012-2031 [Member]	Dec. 31, 2011 Notes (secured, nonrecourse), 4.673% due 2012-2031 [Member]	Dec. 31, 2012 Notes (secured, nonrecourse), 6.00% due 2012-2033 [Member]	Dec. 31, 2011 Notes (secured, nonrecourse), 6.00% due 2012-2033 [Member]	Dec. 31, 2012 Notes (secured, nonrecourse), 5.848% due 2031-2041 [Member]	Dec. 31, 2011 Notes (secured, nonrecourse), 5.848% due 2031-2041 [Member]	Dec. 31, 2012 Notes (secured, nonrecourse) 6.00% due 2021 [Member]	Dec. 31, 2011 Notes (secured, nonrecourse) 6.00% due 2021 [Member]	Dec. 31, 2012 Notes (unsecured), 6.51% due 2013 [Member]	Dec. 31, 2011 Notes (unsecured), 6.51% due 2013 [Member]	Dec. 31, 2012 Notes (unsecured), 6.94% due 2028 [Member]	Dec. 31, 2011 Notes (unsecured), 6.94% due 2028 [Member]	Dec. 31, 2012 Notes (unsecured), 0.504% variable rate due 2016 [Member]	Dec. 31, 2011 Notes (unsecured), 0.504% variable rate due 2016 [Member]	Dec. 31, 2012 Notes (unsecured), 0.504% variable rate due 2030 [Member]	Dec. 31, 2011 Notes (unsecured), 0.504% variable rate due 2030 [Member]	Dec. 31, 2012 Wisconsin Energy Corporation [Member]	Dec. 31, 2011 Wisconsin Energy Corporation [Member]	Dec. 31, 2012 Wisconsin Electric [Member]	Dec. 31, 2011 Wisconsin Electric [Member]	Dec. 31, 2012 Six Per Cent. Preferred Stock [Member] Wisconsin Electric [Member]	Dec. 31, 2011 Six Per Cent. Preferred Stock [Member] Wisconsin Electric [Member]	Dec. 31, 2012 Serial preferred stock, 3.60% Series Redeemable [Member] Wisconsin Electric [Member]	Dec. 31, 2011 Serial preferred stock, 3.60% Series Redeemable [Member] Wisconsin Electric [Member]
Preferred stock, par value																																															$ 0.01	$ 0.01	$ 25	$ 25	$ 100	$ 100	$ 100	$ 100
Preferred stock, shares authorized																																															15,000,000	15,000,000	5,000,000	5,000,000	45,000	45,000	2,286,500	2,286,500
Preferred stock, shares outstanding																																															0	0	0	0	44,498	44,498	260,000	260,000
Preferred stock dividend rate, percentage																																																			6.00%	6.00%	3.60%	3.60%
Preferred stock, redeemable per share																																																					$ 101	$ 101
Debt instrument stated interest rate (percentage)	4.50%	4.50%	6.60%	6.60%	6.00%	6.00%	5.20%	5.20%	6.25%	6.25%	4.25%	4.25%	2.95%	2.95%	6.50%	6.50%	5.625%	5.625%	5.90%	5.90%	5.70%	5.70%	3.65%	3.65%	6.875%	6.875%	4.81%	4.81%	4.91%	4.91%	4.673%	4.673%	6.00%	6.00%	5.848%	5.848%	6.00%	6.00%	6.51%	6.51%	6.94%	6.94%
Long-term debt, percentage bearing variable interest rate																																											0.504%	0.504%	0.504%	0.504%