v3.26.1
Investments in Nuclear Decommissioning Trusts and Other Special Use Funds - Schedule of Investments in Nuclear Decommissioning Trusts and Other Special Use Funds (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Variable Interest Entity | Pinnacle West Captive Insurance Cell          
Nuclear decommissioning trust fund assets          
Special use fund $ 46,000   $ 46,000   $ 40,000
APS          
Nuclear decommissioning trust fund assets          
Total 1,899,827   1,899,827   1,848,993
Total Unrealized Gains     488,251   451,809
Total Unrealized Losses     (16,054)   (14,994)
Amortized cost 1,272,000   1,272,000   1,265,000
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds          
Realized gains 2,659 $ 1,702 7,395 $ 3,360  
Realized losses (4,656) (2,611) (7,453) (5,372)  
Proceeds from the sale of securities 485,393 433,830 997,627 919,644  
APS | Nuclear Decommissioning Trusts          
Nuclear decommissioning trust fund assets          
Total 1,467,958   1,467,958   1,414,166
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds          
Realized gains 2,505 1,702 7,225 3,360  
Realized losses (4,656) (2,611) (7,453) (5,372)  
Proceeds from the sale of securities 403,032 342,313 850,915 758,914  
APS | Other Special Use Funds          
Nuclear decommissioning trust fund assets          
Total 431,869   431,869   434,827
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds          
Realized gains 154 0 170 0  
Realized losses 0 0 0 0  
Proceeds from the sale of securities 82,361 91,517 146,712 160,730  
APS | Captive Insurance Cell          
Nuclear decommissioning trust fund assets          
Total Unrealized Gains     3,700   3,200
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds          
Proceeds from the sale of securities 5,800 $ 25,200 5,800 $ 50,500  
APS | Equity securities          
Nuclear decommissioning trust fund assets          
Equity securities 618,526   618,526   582,135
Total Unrealized Gains     478,401   433,044
Total Unrealized Losses     (6)   (1)
APS | Equity securities | Nuclear Decommissioning Trusts          
Nuclear decommissioning trust fund assets          
Equity securities 563,582   563,582   519,562
APS | Equity securities | Other Special Use Funds          
Nuclear decommissioning trust fund assets          
Equity securities 54,944   54,944   62,573
APS | Equity securities | Other Special Use Funds | Pinnacle West Captive Insurance Cell          
Nuclear decommissioning trust fund assets          
Special use fund 42,200   42,200   40,300
APS | Available for sale-fixed income securities          
Nuclear decommissioning trust fund assets          
Available for sale-fixed income securities 1,265,362   1,265,362   1,267,458
Total Unrealized Gains     9,369   18,765
Total Unrealized Losses     (16,048)   (14,993)
Fair value of fixed income securities, summarized by contractual maturities          
Less than one year 169,807   169,807    
1 year – 5 years 495,063   495,063    
5 years – 10 years 228,670   228,670    
Greater than 10 years 371,822   371,822    
Total 1,265,362   1,265,362    
APS | Available for sale-fixed income securities | Nuclear Decommissioning Trusts          
Nuclear decommissioning trust fund assets          
Available for sale-fixed income securities 895,405   895,405   898,403
Fair value of fixed income securities, summarized by contractual maturities          
Less than one year 28,346   28,346    
1 year – 5 years 282,988   282,988    
5 years – 10 years 212,249   212,249    
Greater than 10 years 371,822   371,822    
Total 895,405   895,405    
APS | Available for sale-fixed income securities | Other Special Use Funds          
Nuclear decommissioning trust fund assets          
Available for sale-fixed income securities 369,957   369,957   369,055
APS | Available for sale-fixed income securities | Coal Reclamation Escrow Account          
Fair value of fixed income securities, summarized by contractual maturities          
Less than one year 101,521   101,521    
1 year – 5 years 56,420   56,420    
5 years – 10 years 0   0    
Greater than 10 years 0   0    
Total 157,941   157,941    
APS | Available for sale-fixed income securities | Active Union Employee Medical Account          
Fair value of fixed income securities, summarized by contractual maturities          
Less than one year 39,940   39,940    
1 year – 5 years 155,655   155,655    
5 years – 10 years 16,421   16,421    
Greater than 10 years 0   0    
Total 212,016   212,016    
APS | Other          
Nuclear decommissioning trust fund assets          
Other 15,939   15,939   (600)
Total Unrealized Gains     481   0
Total Unrealized Losses     0   0
APS | Other | Nuclear Decommissioning Trusts          
Nuclear decommissioning trust fund assets          
Other 8,971   8,971   (3,799)
APS | Other | Other Special Use Funds          
Nuclear decommissioning trust fund assets          
Other 6,968   6,968   $ 3,199
APS | Other | Other Special Use Funds | Pinnacle West Captive Insurance Cell          
Nuclear decommissioning trust fund assets          
Special use fund $ 4,000   $ 4,000