v3.26.1
REGULATORY ENVIRONMENT - PGL QIP RIDER (Details) - USD ($)
$ in Millions
1 Months Ended 3 Months Ended 6 Months Ended
May 31, 2026
Jun. 30, 2026
Dec. 31, 2025
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Aug. 31, 2024
Public Utilities, General Disclosures [Line Items]              
Pre-tax charge to income   $ (328.0)   $ (262.5) $ (1,187.2) $ (1,048.7)  
Reduction in revenues   (2,062.1)   $ (2,009.5) (5,496.3) $ (5,159.0)  
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