Investments in Nuclear Decommissioning Trusts and Other Special Use Funds (Details) - APS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Nuclear decommissioning trust fund assets
Fair Value	$ 1,613,397		$ 1,613,397		$ 1,564,027
Total Unrealized Gains			341,911		358,112
Total Unrealized Losses			(38,947)		(40,868)
Amortized cost	1,185,000		1,185,000		1,120,000
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains	8,943	$ 35,231	63,515	$ 36,441
Realized losses	(3,706)	(11,192)	(6,521)	(16,886)
Proceeds from the sale of securities	328,505	340,902	772,375	567,528
Nuclear Decommissioning Trusts
Nuclear decommissioning trust fund assets
Fair Value	1,245,593		1,245,593		1,201,246
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains	8,943	35,231	63,435	36,441
Realized losses	(3,706)	(11,192)	(6,521)	(16,886)
Proceeds from the sale of securities	270,631	298,761	648,453	434,946
Other Special Use Funds
Nuclear decommissioning trust fund assets
Fair Value	367,804		367,804		362,781
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains	0	0	80	0
Realized losses	0	0	0	0
Proceeds from the sale of securities	57,874	$ 42,141	123,922	$ 132,582
Equity securities
Nuclear decommissioning trust fund assets
Equity securities	454,594		454,594		461,671
Total Unrealized Gains			332,335		336,555
Total Unrealized Losses			0		0
Equity securities | Nuclear Decommissioning Trusts
Nuclear decommissioning trust fund assets
Equity securities	407,805		407,805		420,680
Equity securities | Other Special Use Funds
Nuclear decommissioning trust fund assets
Equity securities	46,789		46,789		40,991
Available for sale-fixed income securities
Nuclear decommissioning trust fund assets
Fair Value	1,155,072		1,155,072		1,100,927
Total Unrealized Gains			9,177		21,518
Total Unrealized Losses			(38,947)		(40,868)
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	113,915		113,915
1 year – 5 years	454,410		454,410
5 years – 10 years	220,325		220,325
Greater than 10 years	366,422		366,422
Total	1,155,072		1,155,072
Available for sale-fixed income securities | Nuclear Decommissioning Trusts
Nuclear decommissioning trust fund assets
Fair Value	836,344		836,344		781,333
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	15,670		15,670
1 year – 5 years	258,628		258,628
5 years – 10 years	195,624		195,624
Greater than 10 years	366,422		366,422
Total	836,344		836,344
Available for sale-fixed income securities | Other Special Use Funds
Nuclear decommissioning trust fund assets
Fair Value	318,728		318,728		319,594
Available for sale-fixed income securities | Coal Reclamation Escrow Account
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	60,841		60,841
1 year – 5 years	43,419		43,419
5 years – 10 years	0		0
Greater than 10 years	0		0
Total	104,260		104,260
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	37,404		37,404
1 year – 5 years	152,363		152,363
5 years – 10 years	24,701		24,701
Greater than 10 years	0		0
Total	214,468		214,468
Other
Nuclear decommissioning trust fund assets
Fair Value	3,731		3,731		1,429
Total Unrealized Gains			399		39
Total Unrealized Losses			0		0
Other | Nuclear Decommissioning Trusts
Nuclear decommissioning trust fund assets
Fair Value	1,444		1,444		(767)
Other | Other Special Use Funds
Nuclear decommissioning trust fund assets
Fair Value	$ 2,287		$ 2,287		$ 2,196