Investments in Nuclear Decommissioning Trusts and Other Special Use Funds (Details) - APS - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Nuclear decommissioning trust fund assets
Fair Value	$ 1,576,507		$ 1,653,167
Total Unrealized Gains	431,150		475,670
Total Unrealized Losses	(36,999)		(4,063)
Amortized cost	991,000		972,000
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains	1,023	$ 2,968
Realized losses	(7,235)	(4,148)
Proceeds from the sale of securities	361,238	379,978
Equity securities
Nuclear decommissioning trust fund assets
Equity securities	611,805		687,882
Total Unrealized Gains	422,497		451,387
Total Unrealized Losses	(37)		0
Available for sale-fixed income securities
Nuclear decommissioning trust fund assets
Fair Value	963,112		992,131
Total Unrealized Gains	8,653		24,283
Total Unrealized Losses	(36,962)		(4,063)
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	100,488
1 year – 5 years	385,820
5 years – 10 years	185,911
Greater than 10 years	290,893
Total	963,112
Other
Nuclear decommissioning trust fund assets
Fair Value	1,590		(26,846)
Total Unrealized Gains	0		0
Total Unrealized Losses	0		0
Nuclear Decommissioning Trusts
Nuclear decommissioning trust fund assets
Fair Value	1,227,465		1,294,757
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains	1,023	2,968
Realized losses	(7,235)	(4,148)
Proceeds from the sale of securities	319,693	234,728
Nuclear Decommissioning Trusts | Equity securities
Nuclear decommissioning trust fund assets
Equity securities	584,737		640,312
Nuclear Decommissioning Trusts | Available for sale-fixed income securities
Nuclear decommissioning trust fund assets
Fair Value	642,250		682,227
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	18,119
1 year – 5 years	198,233
5 years – 10 years	139,957
Greater than 10 years	285,941
Total	642,250
Nuclear Decommissioning Trusts | Other
Nuclear decommissioning trust fund assets
Fair Value	478		(27,782)
Other Special Use Funds
Nuclear decommissioning trust fund assets
Fair Value	349,042		358,410
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains	0	0
Realized losses	0	0
Proceeds from the sale of securities	41,545	$ 145,250
Other Special Use Funds | Equity securities
Nuclear decommissioning trust fund assets
Equity securities	27,068		47,570
Other Special Use Funds | Available for sale-fixed income securities
Nuclear decommissioning trust fund assets
Fair Value	320,862		309,904
Other Special Use Funds | Other
Nuclear decommissioning trust fund assets
Fair Value	1,112		$ 936
Coal Reclamation Escrow Account | Available for sale-fixed income securities
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	41,906
1 year – 5 years	35,749
5 years – 10 years	1,749
Greater than 10 years	4,952
Total	84,356
Active Union Employee Medical Account | Available for sale-fixed income securities
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	40,463
1 year – 5 years	151,838
5 years – 10 years	44,205
Greater than 10 years	0
Total	$ 236,506