Fair Value Measurements - Schedule of Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
ASSETS
Cash equivalents		$ 23
Nuclear decommissioning trusts:	$ 1,414,166	1,282,845
Nuclear decommissioning trust, other	496,793	426,404
Other special use funds:	434,827	408,357
Other special use funds, other	3,199	2,851
Total assets	1,857,380	1,707,783
Total assets, other	489,032	425,485
Commodity contracts
ASSETS
Commodity contracts, other	(10,960)	(3,770)
Derivative asset, total	8,387	16,558
LIABILITIES
Derivative instruments, other	8,399	817
Derivative liability, total	(36,636)	(61,786)
Cash equivalents
ASSETS
Other special use funds:		25,000
Other special use funds, other		0
Equity securities
ASSETS
Nuclear decommissioning trusts:	15,171	15,736
Nuclear decommissioning trust, other	(3,799)	3,335
Other special use funds:	65,772	27,813
Other special use funds, other	3,199	2,851
U.S. commingled equity funds
ASSETS
Nuclear decommissioning trusts:	500,592	423,069
U.S. Treasury debt
ASSETS
Nuclear decommissioning trusts:	364,943	367,396
Other special use funds:	369,055	355,544
Corporate debt
ASSETS
Nuclear decommissioning trusts:	242,176	203,180
Mortgage-backed securities
ASSETS
Nuclear decommissioning trusts:	230,695	208,533
Municipal bonds
ASSETS
Nuclear decommissioning trusts:	37,572	37,429
Other fixed income
ASSETS
Nuclear decommissioning trusts:	23,017	27,502
Level 1
ASSETS
Cash equivalents		23
Nuclear decommissioning trusts:	383,913	379,255
Other special use funds:	431,628	405,506
Total assets	815,541	784,784
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:	40,300	34,200
Level 1 | Cash equivalents
ASSETS
Other special use funds:		25,000
Level 1 | Cash equivalents | Pinnacle West Captive Insurance Cell
ASSETS
Other special use funds:		25,000
Level 1 | Equity securities
ASSETS
Nuclear decommissioning trusts:	18,970	11,859
Other special use funds:	62,573	24,962
Level 1 | Equity securities | Pinnacle West Captive Insurance Cell
ASSETS
Other special use funds:		9,200
Level 1 | U.S. commingled equity funds
ASSETS
Nuclear decommissioning trusts:	0	0
Level 1 | U.S. Treasury debt
ASSETS
Nuclear decommissioning trusts:	364,943	367,396
Other special use funds:	369,055	355,544
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:	533,460	477,186
Other special use funds:	0	0
Total assets	552,807	490,338
Level 2 | Commodity contracts
ASSETS
Commodity contracts	19,347	13,152
LIABILITIES
Derivative instruments	(21,325)	(40,388)
Level 2 | Cash equivalents
ASSETS
Other special use funds:		0
Level 2 | Equity securities
ASSETS
Nuclear decommissioning trusts:	0	542
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:	242,176	203,180
Level 2 | Mortgage-backed securities
ASSETS
Nuclear decommissioning trusts:	230,695	208,533
Level 2 | Municipal bonds
ASSETS
Nuclear decommissioning trusts:	37,572	37,429
Level 2 | Other fixed income
ASSETS
Nuclear decommissioning trusts:	23,017	27,502
Level 3
ASSETS
Cash equivalents		0
Nuclear decommissioning trusts:	0	0
Other special use funds:	0	0
Total assets	0	7,176
Level 3 | Commodity contracts
ASSETS
Commodity contracts	0	7,176
LIABILITIES
Derivative instruments	(23,710)	(22,215)
Level 3 | Cash equivalents
ASSETS
Other special use funds:		0
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:		$ 423,069
Nuclear decommissioning trust, other	$ 500,592