Document and Entity Information (USD $) In Billions, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Jun. 30, 2012
Entity Information [Line Items]
Entity Registrant Name	WISCONSIN ENERGY CORP
Entity Central Index Key	0000783325
Document Type	10-Q
Document Period End Date	Sep. 30, 2012
Amendment Flag	false
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float		$ 9.1
Entity Common Stock, Shares Outstanding (actual number of shares)	230,070,094