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Commitments and Contingencies (Details)
$ in Millions
1 Months Ended 9 Months Ended 148 Months Ended
Oct. 31, 2025
USD ($)
Jan. 01, 2024
USD ($)
trust
Jan. 17, 2023
USD ($)
Jul. 03, 2018
Jul. 31, 2025
USD ($)
Sep. 30, 2025
USD ($)
trust
timePeriod
Oct. 31, 2023
claim
Jul. 11, 2025
operator
Schedule of Commitments and Contingencies [Line Items]                
Production tax credit guarantees           $ 27.0    
Arizona Public Service Company and Palo Verde Owners vs. United States Department of Energy - Spent Nuclear Fuel and Waste Disposal                
Schedule of Commitments and Contingencies [Line Items]                
Settlement amount, awarded to company           $ 174.3    
Arizona Public Service Company and Palo Verde Owners vs. United States Department of Energy - Spent Nuclear Fuel and Waste Disposal | Subsequent Event                
Schedule of Commitments and Contingencies [Line Items]                
Settlement amount, sought $ 15.4              
APS                
Schedule of Commitments and Contingencies [Line Items]                
Maximum insurance against public liability per occurrence for a nuclear incident   $ 16,300.0            
Maximum available nuclear liability insurance   500.0            
Remaining nuclear liability insurance through mandatory industry wide retrospective assessment program   15,800.0            
Maximum assessment per reactor for each nuclear incident   165.9            
Annual limit per incident with respect to maximum assessment   $ 24.7            
Number of VIE lessor trusts | trust   3       3    
Maximum potential retrospective assessment per incident of APS   $ 144.9            
Annual payment limitation with respect to maximum potential retrospective assessment   $ 21.6            
Amount of "all risk" (including nuclear hazards) insurance for property damage to, and decontamination of, property at Palo Verde           $ 2,800.0    
Request second-year energy price for exported energy           24.2    
Collateral assurance based on rating triggers           $ 66.4    
Period to provide collateral assurance based on rating triggers           20 days    
Number of power plant operators | operator               25
Purchase commitment, amount         $ 7,300.0      
Purchase commitment, period         25 years      
APS | Surety Bonds Expiring in 2028                
Schedule of Commitments and Contingencies [Line Items]                
Surety bonds expiring, amount           $ 23.4    
APS | Letter of Credit                
Schedule of Commitments and Contingencies [Line Items]                
Outstanding letters of credit           33.2    
APS | Contaminated Groundwater Wells                
Schedule of Commitments and Contingencies [Line Items]                
Costs related to investigation and study under Superfund site           3.0    
Remedial investigation work     $ 1.7          
APS | Contaminated Groundwater Wells | Pending Litigation                
Schedule of Commitments and Contingencies [Line Items]                
Settlement amount           $ 8.3    
APS | Arizona Public Service Company and Palo Verde Owners vs. United States Department of Energy - Spent Nuclear Fuel and Waste Disposal                
Schedule of Commitments and Contingencies [Line Items]                
Number of claims submitted | claim             11  
Gain contingency, number of settlement agreement time periods | timePeriod           11    
Settlement amount, awarded to company           $ 50.7    
APS | Arizona Public Service Company and Palo Verde Owners vs. United States Department of Energy - Spent Nuclear Fuel and Waste Disposal | Subsequent Event                
Schedule of Commitments and Contingencies [Line Items]                
Settlement amount, sought $ 4.5              
NTEC | Four Corners                
Schedule of Commitments and Contingencies [Line Items]                
Asset purchase agreement, option to purchase, ownership interest, percentage       7.00%