Condensed Parent Company Financial Statements (Details 5) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Condensed Parent Company Financial Statements (Textuals) [Abstract]
Issuance of new notes and the proceeds used to repay short-term debt	$ 20.3	$ 466.6	$ 291.7
Issuance of Junior Notes	251.8	720.0	530.0
Restriction under RCC	The RCC provides that we may not redeem, defease or purchase and our subsidiaries may not purchase any Junior Notes on or before May 15, 2037, unless, subject to certain limitations described in the RCC, during the 180 days prior to the date of redemption, defeasance or purchase, we have received a specified amount of proceeds from the sale of qualifying securities.
Interest paid, net of amounts capitalized	241.2	234.0	198.0
Net refunds from income taxes	107.0	109.1
Wisconsin Energy Corporation [Member]
Condensed Parent Company Financial Statements (Textuals) [Abstract]
Long-term notes outstanding of WECC	80
Issuance of new notes and the proceeds used to repay short-term debt	0	450.0	281.5
Minimum Total Funded Debt to Capitalization Ratio, As a Percent	70.00%
Interest paid, net of amounts capitalized	45.2	57.7	43.5
Net refunds from income taxes	128.2	114.6	1.0
Wisconsin Electric and Wisconsin Gas [Member]
Condensed Parent Company Financial Statements (Textuals) [Abstract]
Dividends and distributions from subsidiaries	212.6
We Power [Member]
Condensed Parent Company Financial Statements (Textuals) [Abstract]
Dividends and distributions from subsidiaries	$ 629.7
Notes (unsecured), 6.20% due 2033 [Member]
Condensed Parent Company Financial Statements (Textuals) [Abstract]
Debt instrument interest rate stated percentage rate	6.20%	6.20%
Junior Notes (unsecured), 6.25% due 2067 [Member]
Condensed Parent Company Financial Statements (Textuals) [Abstract]
Debt instrument interest rate stated percentage rate	6.25%	6.25%