v3.26.1
LONG-TERM DEBT - CONVERTIBLE DEBT (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Debt Instrument [Line Items]        
Interest expense $ 228.9 $ 220.8 $ 457.4 $ 443.8
WEC Energy Group | WEC 4.375% Convertible Notes due June 1, 2027        
Debt Instrument [Line Items]        
Senior Notes 862.5   862.5  
Unamortized debt issuance costs (3.0)   (3.0)  
Net carrying amount 859.5   859.5  
Fair value amount 1,044.2   1,044.2  
Contractual interest expense 9.5 9.5 18.9 18.9
Amortization of debt issuance costs 0.9 0.9 1.7 1.7
Interest expense 10.4 10.4 20.6 20.6
WEC Energy Group | WEC 3.375% Convertible Notes due June 1, 2028        
Debt Instrument [Line Items]        
Senior Notes 900.0   900.0  
Unamortized debt issuance costs (6.8)   (6.8)  
Net carrying amount 893.2   893.2  
Fair value amount 936.0   936.0  
Contractual interest expense 7.6 1.8 15.2 1.8
Amortization of debt issuance costs 0.9 0.3 1.8 0.3
Interest expense 8.5 2.1 17.0 2.1
WEC Energy Group | WEC 4.375% Convertible Notes due June 1, 2029        
Debt Instrument [Line Items]        
Senior Notes 862.5   862.5  
Unamortized debt issuance costs (5.8)   (5.8)  
Net carrying amount 856.7   856.7  
Fair value amount 1,069.2   1,069.2  
Contractual interest expense 9.5 9.5 18.9 18.9
Amortization of debt issuance costs 0.5 0.5 1.0 1.0
Interest expense $ 10.0 $ 10.0 $ 19.9 $ 19.9