v3.25.1
Fair Value Measurements - Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($)
$ in Thousands
Mar. 31, 2025
Dec. 31, 2024
ASSETS    
Cash equivalents $ 23 $ 23
Nuclear decommissioning trust 1,286,101 1,282,845
Nuclear decommissioning trust, other 407,953 426,404
Other special use fund 415,401 408,357
Other special use funds, other 2,030 2,851
Total assets 1,810,450 1,707,783
Total assets, other 407,672 425,485
Commodity contracts    
ASSETS    
Commodity contracts, assets 108,925 16,558
Commodity contracts assets, other (2,311) (3,770)
LIABILITIES    
Derivative instruments, other (1,880) 817
Derivative instruments, total (27,576) (61,786)
Equity securities    
ASSETS    
Nuclear decommissioning trust 14,180 15,736
Nuclear decommissioning trust, other 2,690 3,335
Other special use fund 39,264 27,813
Other special use funds, other 2,030 2,851
U.S. commingled equity funds    
ASSETS    
Nuclear decommissioning trust 405,263 423,069
U.S. Treasury debt    
ASSETS    
Nuclear decommissioning trust 359,911 367,396
Other special use fund 376,137 355,544
Corporate debt    
ASSETS    
Nuclear decommissioning trust 220,641 203,180
Mortgage-backed securities    
ASSETS    
Nuclear decommissioning trust 224,983 208,533
Municipal bonds    
ASSETS    
Nuclear decommissioning trust 33,817 37,429
Other fixed income    
ASSETS    
Nuclear decommissioning trust 27,306 27,502
Cash equivalents    
ASSETS    
Other special use fund   25,000
Other special use funds, other   0
Level 1    
ASSETS    
Cash equivalents 23 23
Nuclear decommissioning trust 371,401 379,255
Other special use fund 413,371 405,506
Total assets 784,795 784,784
Level 1 | Pinnacle West Captive Insurance Cell    
ASSETS    
Other special use fund 35,100 34,200
Level 1 | Commodity contracts    
ASSETS    
Commodity contracts, assets 0 0
LIABILITIES    
Derivative instruments 0 0
Level 1 | Equity securities    
ASSETS    
Nuclear decommissioning trust 11,490 11,859
Other special use fund 37,234 24,962
Level 1 | Equity securities | Pinnacle West Captive Insurance Cell    
ASSETS    
Other special use fund 10,000 9,200
Level 1 | U.S. commingled equity funds    
ASSETS    
Nuclear decommissioning trust 0 0
Level 1 | U.S. Treasury debt    
ASSETS    
Nuclear decommissioning trust 359,911 367,396
Other special use fund 376,137 355,544
Level 1 | U.S. Treasury debt | Pinnacle West Captive Insurance Cell    
ASSETS    
Other special use fund 25,100  
Level 1 | Corporate debt    
ASSETS    
Nuclear decommissioning trust 0 0
Level 1 | Mortgage-backed securities    
ASSETS    
Nuclear decommissioning trust 0 0
Level 1 | Municipal bonds    
ASSETS    
Nuclear decommissioning trust 0 0
Level 1 | Other fixed income    
ASSETS    
Nuclear decommissioning trust 0 0
Level 1 | Cash equivalents    
ASSETS    
Other special use fund   25,000
Level 1 | Cash equivalents | Pinnacle West Captive Insurance Cell    
ASSETS    
Other special use fund   25,000
Level 2    
ASSETS    
Cash equivalents 0 0
Nuclear decommissioning trust 506,747 477,186
Other special use fund 0 0
Total assets 616,794 490,338
Level 2 | Commodity contracts    
ASSETS    
Commodity contracts, assets 110,047 13,152
LIABILITIES    
Derivative instruments (1,667) (40,388)
Level 2 | Equity securities    
ASSETS    
Nuclear decommissioning trust 0 542
Other special use fund 0 0
Level 2 | U.S. commingled equity funds    
ASSETS    
Nuclear decommissioning trust 0 0
Level 2 | U.S. Treasury debt    
ASSETS    
Nuclear decommissioning trust 0 0
Other special use fund 0 0
Level 2 | Corporate debt    
ASSETS    
Nuclear decommissioning trust 220,641 203,180
Level 2 | Mortgage-backed securities    
ASSETS    
Nuclear decommissioning trust 224,983 208,533
Level 2 | Municipal bonds    
ASSETS    
Nuclear decommissioning trust 33,817 37,429
Level 2 | Other fixed income    
ASSETS    
Nuclear decommissioning trust 27,306 27,502
Level 2 | Cash equivalents    
ASSETS    
Other special use fund   0
Level 3    
ASSETS    
Cash equivalents 0 0
Nuclear decommissioning trust 0 0
Other special use fund 0 0
Total assets 1,189 7,176
Level 3 | Commodity contracts    
ASSETS    
Commodity contracts, assets 1,189 7,176
LIABILITIES    
Derivative instruments (24,029) (22,215)
Level 3 | Equity securities    
ASSETS    
Nuclear decommissioning trust 0 0
Other special use fund 0 0
Level 3 | U.S. commingled equity funds    
ASSETS    
Nuclear decommissioning trust 0 0
Level 3 | U.S. Treasury debt    
ASSETS    
Nuclear decommissioning trust 0 0
Other special use fund 0 0
Level 3 | Corporate debt    
ASSETS    
Nuclear decommissioning trust 0 0
Level 3 | Mortgage-backed securities    
ASSETS    
Nuclear decommissioning trust 0 0
Level 3 | Municipal bonds    
ASSETS    
Nuclear decommissioning trust 0 0
Level 3 | Other fixed income    
ASSETS    
Nuclear decommissioning trust 0 0
Level 3 | Cash equivalents    
ASSETS    
Other special use fund   0
Fair Value Measured at Net Asset Value Per Share | U.S. commingled equity funds    
ASSETS    
Nuclear decommissioning trust $ 405,263 $ 423,069