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Regulatory Matters - SPPC - Narrative (Details) - USD ($)
$ in Millions
1 Months Ended
Jan. 31, 2025
Sep. 30, 2024
Jun. 30, 2024
Feb. 29, 2024
Dec. 31, 2024
Dec. 31, 2023
Public Utilities, General Disclosures [Line Items]            
Regulatory assets not earning a return on investment         $ 2,100 $ 3,200
SPPC            
Public Utilities, General Disclosures [Line Items]            
Regulatory assets not earning a return on investment         $ 131 $ 132
SPPC | PUNC | Subsequent event            
Public Utilities, General Disclosures [Line Items]            
Requested self insurance policy, amount $ 500          
Requested self insurance policy, period 10 years          
SPPC | PUNC | Electric            
Public Utilities, General Disclosures [Line Items]            
Requested rate increase (decrease)     $ 96 $ 95    
Requested rate increase (decrease), percentage     9.50% 8.80%    
Approved rate increase (decrease)   $ 40        
SPPC | PUNC | Natural gas            
Public Utilities, General Disclosures [Line Items]            
Requested rate increase (decrease)     $ 12 $ 11    
Requested rate increase (decrease), percentage     6.40% 4.90%    
Approved rate increase (decrease)   $ 8