Investments in Nuclear Decommissioning Trusts and Other Special Use Funds - Schedule of Investments in Nuclear Decommissioning Trusts and Other Special Use Funds (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Variable Interest Entity | Pinnacle West Captive Insurance Cell
Fair value of fixed income securities, summarized by contractual maturities
Special use fund	$ 39,000		$ 39,000		$ 34,000
APS
Nuclear decommissioning trust fund assets
Total	1,823,378		1,823,378		1,691,202
Total Unrealized Gains			440,645		366,844
Total Unrealized Losses			(14,982)		(32,136)
Amortized cost	1,205,000		1,205,000		1,224,000
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains	3,972	$ 3,825	7,332	$ 67,340
Realized losses	(2,184)	(4,162)	(7,556)	(10,683)
Proceeds from the sale of securities	455,515	367,996	1,375,159	1,140,371
Fair value of fixed income securities, summarized by contractual maturities
Special use fund					34,200
APS | Nuclear Decommissioning Trusts
Nuclear decommissioning trust fund assets
Total	1,393,446		1,393,446		1,282,845
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains	3,730	3,825	7,090	67,260
Realized losses	(2,184)	(4,162)	(7,556)	(10,683)
Proceeds from the sale of securities	357,399	293,758	1,116,313	942,211
APS | Other Special Use Funds
Nuclear decommissioning trust fund assets
Total	429,932		429,932		408,357
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains	242	0	242	80
Realized losses	0	0	0	0
Proceeds from the sale of securities	98,116	$ 74,238	258,846	$ 198,160
APS | Captive Insurance Cell
Nuclear decommissioning trust fund assets
Total Unrealized Gains			2,500
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Proceeds from the sale of securities			50,500
APS | Equity securities
Nuclear decommissioning trust fund assets
Equity securities	610,185		610,185		460,432
Total Unrealized Gains			421,222		359,127
Total Unrealized Losses			0		(176)
APS | Equity securities | Nuclear Decommissioning Trusts
Nuclear decommissioning trust fund assets
Equity securities	506,831		506,831		435,470
APS | Equity securities | Other Special Use Funds
Nuclear decommissioning trust fund assets
Equity securities	103,354		103,354		24,962
APS | Available for sale-fixed income securities
Nuclear decommissioning trust fund assets
Available for sale-fixed income securities	1,208,935		1,208,935		1,199,584
Total Unrealized Gains			19,423		7,717
Total Unrealized Losses			(14,982)		(31,960)
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	174,969		174,969
1 year – 5 years	455,343		455,343
5 years – 10 years	166,081		166,081
Greater than 10 years	412,542		412,542
Total	1,208,935		1,208,935
APS | Available for sale-fixed income securities | Nuclear Decommissioning Trusts
Nuclear decommissioning trust fund assets
Available for sale-fixed income securities	884,524		884,524		844,040
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	34,450		34,450
1 year – 5 years	271,451		271,451
5 years – 10 years	166,081		166,081
Greater than 10 years	412,542		412,542
Total	884,524		884,524
APS | Available for sale-fixed income securities | Other Special Use Funds
Nuclear decommissioning trust fund assets
Available for sale-fixed income securities	324,411		324,411		355,544
APS | Available for sale-fixed income securities | Coal Reclamation Escrow Account
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	101,134		101,134
1 year – 5 years	48,192		48,192
5 years – 10 years	0		0
Greater than 10 years	0		0
Total	149,326		149,326
APS | 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	39,385		39,385
1 year – 5 years	135,700		135,700
5 years – 10 years	0		0
Greater than 10 years	0		0
Total	175,085		175,085
APS | Other
Nuclear decommissioning trust fund assets
Other	4,258		4,258		31,186
Total Unrealized Gains			0		0
Total Unrealized Losses			0		0
APS | Other | Nuclear Decommissioning Trusts
Nuclear decommissioning trust fund assets
Other	2,091		2,091		3,335
APS | Other | Other Special Use Funds
Nuclear decommissioning trust fund assets
Other	2,167		2,167		$ 27,851
Pinnacle West | Variable Interest Entity | Pinnacle West Captive Insurance Cell
Fair value of fixed income securities, summarized by contractual maturities
Special use fund	$ 39,400		$ 39,400