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Cover Page - USD ($)
$ in Billions
 12 Months Ended
Dec. 31, 2019
Jan. 31, 2020
Jun. 30, 2019
Cover page.      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2019    
Document Transition Report false    
Entity File Number 001-09057    
Entity Registrant Name WEC ENERGY GROUP, INC.    
Entity Tax Identification Number 39-1391525    
Entity Incorporation, State or Country Code WI    
Entity Address, Address Line One 231 West Michigan Street    
Entity Address, Address Line Two P.O. Box 1331    
Entity Address, City or Town Milwaukee    
Entity Address, State or Province WI    
Entity Address, Postal Zip Code 53201    
City Area Code 414    
Local Phone Number 221-2345    
Title of 12(b) Security Common Stock, $.01 Par Value    
Trading Symbol WEC    
Security Exchange Name NYSE    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Shell Company false    
Entity Public Float     $ 26.3
Entity Common Stock, Shares Outstanding   315,434,531  
Documents Incorporated by Reference
Portions of WEC Energy Group, Inc.'s Definitive Proxy Statement on Schedule 14A for its Annual Meeting of Shareholders, to be held on May 6, 2020, are incorporated by reference into Part III hereof.
    
Entity Central Index Key 0000783325    
Current Fiscal Year End Date --12-31    
Document Fiscal Year Focus 2019    
Document Fiscal Period Focus FY    
Amendment Flag false