v3.26.1
Fair Value Measurements - Schedule of Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
ASSETS    
Cash equivalents $ 103  
Nuclear decommissioning trusts: 1,467,958 $ 1,414,166
Nuclear decommissioning trust, other 558,339 496,793
Other special use funds: 431,869 434,827
Other special use funds, other 6,968 3,199
Total assets 1,899,935 1,857,380
Total assets, other 563,300 489,032
Commodity contracts    
ASSETS    
Commodity contracts, other (2,007) (10,960)
Derivative asset, total 5 8,387
LIABILITIES    
Derivative instruments, other (284) 8,399
Derivative liability, total (81,127) (36,636)
Equity securities    
ASSETS    
Nuclear decommissioning trusts: 23,185 15,171
Nuclear decommissioning trust, other 8,971 (3,799)
Other special use funds: 61,912 65,772
Other special use funds, other 6,968 3,199
U.S. commingled equity funds    
ASSETS    
Nuclear decommissioning trusts: 549,368 500,592
U.S. Treasury debt    
ASSETS    
Nuclear decommissioning trusts: 394,337 364,943
Other special use funds: 369,957 369,055
Corporate debt    
ASSETS    
Nuclear decommissioning trusts: 250,143 242,176
Mortgage-backed securities    
ASSETS    
Nuclear decommissioning trusts: 213,368 230,695
Municipal bonds    
ASSETS    
Nuclear decommissioning trusts: 18,146 37,572
Other fixed income    
ASSETS    
Nuclear decommissioning trusts: 19,411 23,017
Other equity securities    
ASSETS    
Other special use funds: 4,000  
Level 1    
ASSETS    
Cash equivalents 103  
Nuclear decommissioning trusts: 408,551 383,913
Other special use funds: 424,901 431,628
Total assets 833,555 815,541
Level 1 | Commodity contracts    
ASSETS    
Commodity contracts 0 0
LIABILITIES    
Derivative instruments 0 0
Level 1 | Pinnacle West Captive Insurance Cell    
ASSETS    
Other special use funds: 42,200 40,300
Level 1 | Equity securities    
ASSETS    
Nuclear decommissioning trusts: 14,214 18,970
Other special use funds: 54,944 62,573
Level 1 | U.S. commingled equity funds    
ASSETS    
Nuclear decommissioning trusts: 0 0
Level 1 | U.S. Treasury debt    
ASSETS    
Nuclear decommissioning trusts: 394,337 364,943
Other special use funds: 369,957 369,055
Level 1 | Corporate debt    
ASSETS    
Nuclear decommissioning trusts: 0 0
Level 1 | Mortgage-backed securities    
ASSETS    
Nuclear decommissioning trusts: 0 0
Level 1 | Municipal bonds    
ASSETS    
Nuclear decommissioning trusts: 0 0
Level 1 | Other fixed income    
ASSETS    
Nuclear decommissioning trusts: 0 0
Level 2    
ASSETS    
Cash equivalents 0  
Nuclear decommissioning trusts: 501,068 533,460
Other special use funds: 0 0
Total assets 502,812 552,807
Level 2 | Commodity contracts    
ASSETS    
Commodity contracts 1,744 19,347
LIABILITIES    
Derivative instruments (47,713) (21,325)
Level 2 | Equity securities    
ASSETS    
Nuclear decommissioning trusts: 0 0
Other special use funds: 0 0
Level 2 | U.S. commingled equity funds    
ASSETS    
Nuclear decommissioning trusts: 0 0
Level 2 | U.S. Treasury debt    
ASSETS    
Nuclear decommissioning trusts: 0 0
Other special use funds: 0 0
Level 2 | Corporate debt    
ASSETS    
Nuclear decommissioning trusts: 250,143 242,176
Level 2 | Mortgage-backed securities    
ASSETS    
Nuclear decommissioning trusts: 213,368 230,695
Level 2 | Municipal bonds    
ASSETS    
Nuclear decommissioning trusts: 18,146 37,572
Level 2 | Other fixed income    
ASSETS    
Nuclear decommissioning trusts: 19,411 23,017
Level 3    
ASSETS    
Cash equivalents 0  
Nuclear decommissioning trusts: 0 0
Other special use funds: 0 0
Total assets 268 0
Level 3 | Commodity contracts    
ASSETS    
Commodity contracts 268 0
LIABILITIES    
Derivative instruments (33,130) (23,710)
Level 3 | Equity securities    
ASSETS    
Nuclear decommissioning trusts: 0 0
Other special use funds: 0 0
Level 3 | U.S. commingled equity funds    
ASSETS    
Nuclear decommissioning trusts: 0 0
Level 3 | U.S. Treasury debt    
ASSETS    
Nuclear decommissioning trusts: 0 0
Other special use funds: 0 0
Level 3 | Corporate debt    
ASSETS    
Nuclear decommissioning trusts: 0 0
Level 3 | Mortgage-backed securities    
ASSETS    
Nuclear decommissioning trusts: 0 0
Level 3 | Municipal bonds    
ASSETS    
Nuclear decommissioning trusts: 0 0
Level 3 | Other fixed income    
ASSETS    
Nuclear decommissioning trusts: 0 0
Fair Value Measured at Net Asset Value Per Share | U.S. commingled equity funds    
ASSETS    
Nuclear decommissioning trusts:   $ 500,592
Nuclear decommissioning trust, other $ 549,368