Condensed Parent Company Financial Statements (Details 4) (USD $)	Dec. 31, 2011
Various guarantees to provide financial and performance assurance to third parties on behalf of affiliates
Guarantees, Maximum Potential Future Payments	$ 2,700,000
Guarantees, Outstanding	100,000
Liability	0
Wisconsin Energy Corporation [Member]
Various guarantees to provide financial and performance assurance to third parties on behalf of affiliates
Guarantees, Maximum Potential Future Payments	68,300,000
Guarantees, Outstanding	9,900,000
Liability	0
Letters of Credit [Member] | Wisconsin Energy Corporation [Member]
Various guarantees to provide financial and performance assurance to third parties on behalf of affiliates
Guarantees, Maximum Potential Future Payments	400,000
Guarantees, Outstanding	400,000
Liability	0
Utility Energy [Member] | Wisconsin Energy Corporation [Member]
Various guarantees to provide financial and performance assurance to third parties on behalf of affiliates
Guarantees, Maximum Potential Future Payments	9,900,000
Guarantees, Outstanding	9,900,000
Liability	0
Non-Utility Energy [Member] | Wisconsin Energy Corporation [Member]
Various guarantees to provide financial and performance assurance to third parties on behalf of affiliates
Guarantees, Maximum Potential Future Payments	58,100,000
Guarantees, Outstanding	0
Liability	0
Corporate and Other [Member] | Wisconsin Energy Corporation [Member]
Various guarantees to provide financial and performance assurance to third parties on behalf of affiliates
Guarantees, Maximum Potential Future Payments	300,000
Guarantees, Outstanding	0
Liability	$ 0