Fair Value Measurements - Schedule of Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
ASSETS
Nuclear decommissioning trusts:	$ 1,392,817	$ 1,414,166
Nuclear decommissioning trust, other	482,327	496,793
Other special use funds:	437,745	434,827
Other special use funds, other	2,012	3,199
Total assets	1,831,416	1,857,380
Total assets, other	474,051	489,032
Commodity contracts
ASSETS
Commodity contracts, other	(10,288)	(10,960)
Derivative asset, total	854	8,387
LIABILITIES
Derivative instruments, other	7,727	8,399
Derivative liability, total	(61,637)	(36,636)
Equity securities
ASSETS
Nuclear decommissioning trusts:	22,098	15,171
Nuclear decommissioning trust, other	3,557	(3,799)
Other special use funds:	66,862	65,772
Other special use funds, other	2,012	3,199
U.S. commingled equity funds
ASSETS
Nuclear decommissioning trusts:	478,770	500,592
U.S. Treasury debt
ASSETS
Nuclear decommissioning trusts:	369,970	364,943
Other special use funds:	370,883	369,055
Corporate debt
ASSETS
Nuclear decommissioning trusts:	249,372	242,176
Mortgage-backed securities
ASSETS
Nuclear decommissioning trusts:	217,924	230,695
Municipal bonds
ASSETS
Nuclear decommissioning trusts:	34,288	37,572
Other fixed income
ASSETS
Nuclear decommissioning trusts:	20,395	23,017
Level 1
ASSETS
Nuclear decommissioning trusts:	388,511	383,913
Other special use funds:	435,733	431,628
Total assets	824,244	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:	41,400	40,300
Level 1 | Equity securities
ASSETS
Nuclear decommissioning trusts:	18,541	18,970
Other special use funds:	64,850	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:	369,970	364,943
Other special use funds:	370,883	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
Nuclear decommissioning trusts:	521,979	533,460
Other special use funds:	0	0
Total assets	533,121	552,807
Level 2 | Commodity contracts
ASSETS
Commodity contracts	11,142	19,347
LIABILITIES
Derivative instruments	(35,908)	(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:	249,372	242,176
Level 2 | Mortgage-backed securities
ASSETS
Nuclear decommissioning trusts:	217,924	230,695
Level 2 | Municipal bonds
ASSETS
Nuclear decommissioning trusts:	34,288	37,572
Level 2 | Other fixed income
ASSETS
Nuclear decommissioning trusts:	20,395	23,017
Level 3
ASSETS
Nuclear decommissioning trusts:	0	0
Other special use funds:	0	0
Total assets	0	0
Level 3 | Commodity contracts
ASSETS
Commodity contracts	0	0
LIABILITIES
Derivative instruments	(33,456)	(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	$ 478,770