v3.26.1
REGULATORY ENVIRONMENT - PGL AND NSG UEA RIDER (Details)
$ in Millions
1 Months Ended 3 Months Ended 6 Months Ended
May 31, 2026
USD ($)
Jun. 30, 2026
USD ($)
Dec. 31, 2025
USD ($)
Jun. 30, 2025
USD ($)
Jun. 30, 2026
USD ($)
Jun. 30, 2025
USD ($)
Public Utilities, General Disclosures [Line Items]            
Reduction in revenues   $ (2,062.1)   $ (2,009.5) $ (5,496.3) $ (5,159.0)
Illinois Commerce Commission (ICC) | UEA Rider Settlement Terms            
Public Utilities, General Disclosures [Line Items]            
Refund period 3 years          
Reduction in revenues     $ 50.0      
Illinois Commerce Commission (ICC) | UEA Rider Settlement Terms | 2026            
Public Utilities, General Disclosures [Line Items]            
Percentage to be refunded to customers each year 0.50          
Illinois Commerce Commission (ICC) | UEA Rider Settlement Terms | 2027            
Public Utilities, General Disclosures [Line Items]            
Percentage to be refunded to customers each year 0.25          
Illinois Commerce Commission (ICC) | UEA Rider Settlement Terms | 2028            
Public Utilities, General Disclosures [Line Items]            
Percentage to be refunded to customers each year 0.25          
Illinois Commerce Commission (ICC) | PGL | UEA Rider Settlement Terms            
Public Utilities, General Disclosures [Line Items]            
Refunds required to customers $ 49.0          
Illinois Commerce Commission (ICC) | NSG | UEA Rider Settlement Terms            
Public Utilities, General Disclosures [Line Items]            
Refunds required to customers $ 1.0