Investments in Nuclear Decommissioning Trusts and Other Special Use Funds (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
	Jan. 04, 2021	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Subsequent Event
Fair value of fixed income securities, summarized by contractual maturities
Transfer to active union medical account	$ 106,000
ARIZONA PUBLIC SERVICE COMPANY
Nuclear decommissioning trust fund assets
Fair Value		$ 1,392,944	$ 1,392,944	$ 1,255,870
Total Unrealized Gains		468,247	468,247	363,476
Total Unrealized Losses		(398)	(398)	(669)
Amortized cost		687,000	687,000	691,000
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains			12,370	11,132	$ 6,680
Realized losses			(5,568)	(6,972)	(13,552)
Proceeds from the sale of securities			819,519	719,034	653,033
Fair value of fixed income securities, summarized by contractual maturities
Employee medical claims amount		14,000		15,000
ARIZONA PUBLIC SERVICE COMPANY | Equity securities
Nuclear decommissioning trust fund assets
Equity Securities		677,188	677,188	536,858
Total Unrealized Gains		421,666	421,666	337,681
Total Unrealized Losses		0	0	0
ARIZONA PUBLIC SERVICE COMPANY | Fixed income securities
Nuclear decommissioning trust fund assets
Fair Value		733,080	733,080	716,137
Total Unrealized Gains		46,581	46,581	25,795
Total Unrealized Losses		(398)	(398)	(669)
Fair value of fixed income securities, summarized by contractual maturities
Less than one year		52,642	52,642
1 year - 5 years		323,570	323,570
5 years - 10 years		136,045	136,045
Greater than 10 years		220,823	220,823
Total		733,080	733,080
ARIZONA PUBLIC SERVICE COMPANY | Other Receivables from Broker-Dealers and Clearing
Nuclear decommissioning trust fund assets
Other		(17,324)	(17,324)	2,875
Total Unrealized Gains		0	0	0
Total Unrealized Losses		0	0	0
Nuclear Decommissioning Trusts | ARIZONA PUBLIC SERVICE COMPANY
Nuclear decommissioning trust fund assets
Fair Value		1,138,435	1,138,435	1,010,775
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains			12,194	11,024	6,679
Realized losses			(5,553)	(6,972)	(13,552)
Proceeds from the sale of securities			675,035	473,806	554,385
Nuclear Decommissioning Trusts | ARIZONA PUBLIC SERVICE COMPANY | Equity securities
Nuclear decommissioning trust fund assets
Equity Securities		639,851	639,851	529,716
Nuclear Decommissioning Trusts | ARIZONA PUBLIC SERVICE COMPANY | Fixed income securities
Nuclear decommissioning trust fund assets
Fair Value		516,412	516,412	478,658
Fair value of fixed income securities, summarized by contractual maturities
Less than one year		19,563	19,563
1 year - 5 years		151,537	151,537
5 years - 10 years		133,307	133,307
Greater than 10 years		212,005	212,005
Total		516,412	516,412
Nuclear Decommissioning Trusts | ARIZONA PUBLIC SERVICE COMPANY | Other Receivables from Broker-Dealers and Clearing
Nuclear decommissioning trust fund assets
Other		(17,828)	(17,828)	2,401
Coal Reclamation Escrow Account | ARIZONA PUBLIC SERVICE COMPANY | Fixed income securities
Fair value of fixed income securities, summarized by contractual maturities
Less than one year		33,079	33,079
1 year - 5 years		29,722	29,722
5 years - 10 years		2,738	2,738
Greater than 10 years		8,818	8,818
Total		74,357	74,357
Active union medical trust | ARIZONA PUBLIC SERVICE COMPANY | Fixed income securities
Fair value of fixed income securities, summarized by contractual maturities
Less than one year		0	0
1 year - 5 years		142,311	142,311
5 years - 10 years		0	0
Greater than 10 years		0	0
Total		142,311	142,311
Other Special Use Funds | ARIZONA PUBLIC SERVICE COMPANY
Nuclear decommissioning trust fund assets
Fair Value		254,509	254,509	245,095
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains			176	108	1
Realized losses			(15)	0	0
Proceeds from the sale of securities			144,484	245,228	$ 98,648
Other Special Use Funds | ARIZONA PUBLIC SERVICE COMPANY | Equity securities
Nuclear decommissioning trust fund assets
Equity Securities		37,337	37,337	7,142
Other Special Use Funds | ARIZONA PUBLIC SERVICE COMPANY | Fixed income securities
Nuclear decommissioning trust fund assets
Fair Value		216,668	216,668	237,479
Other Special Use Funds | ARIZONA PUBLIC SERVICE COMPANY | Other Receivables from Broker-Dealers and Clearing
Nuclear decommissioning trust fund assets
Other		$ 504	$ 504	$ 474