v3.26.3
REGULATORY ENVIRONMENT - PGL QIP RIDER (Details) - USD ($)
$ in Millions
1 Months Ended 3 Months Ended 9 Months Ended
May 31, 2026
Sep. 30, 2026
Dec. 31, 2025
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Aug. 31, 2024
Public Utilities, General Disclosures [Line Items]              
Pre-tax charge to income   $ (437.3)   $ (304.6) $ (1,624.5) $ (1,353.3)  
Reduction in revenues   (2,290.6)   $ (2,104.0) (7,786.9) $ (7,263.0)  
PGL              
Public Utilities, General Disclosures [Line Items]              
Impairments related to Illinois segment     $ 130.0        
Illinois Commerce Commission (ICC) | PGL | 2016 Annual QIP Rider Reconciliation              
Public Utilities, General Disclosures [Line Items]              
Disallowed capital costs             $ 14.8
Illinois Commerce Commission (ICC) | PGL | QIP Settlement              
Public Utilities, General Disclosures [Line Items]              
Qualified infrastructure investment costs to be removed from rate base $ 130.0            
Refunds required to customers $ 75.0            
Refund period 3 years            
Pre-tax charge to income     155.0        
Impairments related to Illinois segment     130.0        
Reduction in revenues     $ 25.0        
Total balance sheet impact recorded   205.0     205.0    
Charge to income recorded in prior years   $ 50.0     $ 50.0    
Illinois Commerce Commission (ICC) | PGL | QIP Settlement | 2026              
Public Utilities, General Disclosures [Line Items]              
Amount to be refunded to customers each year $ 25.0            
Illinois Commerce Commission (ICC) | PGL | QIP Settlement | 2027              
Public Utilities, General Disclosures [Line Items]              
Amount to be refunded to customers each year 25.0            
Illinois Commerce Commission (ICC) | PGL | QIP Settlement | 2028              
Public Utilities, General Disclosures [Line Items]              
Amount to be refunded to customers each year $ 25.0