Investments in Nuclear Decommissioning Trusts and Other Special Use Funds (Details) - ARIZONA PUBLIC SERVICE COMPANY - USD ($) $ in Thousands		12 Months Ended
	Aug. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Nuclear decommissioning trust fund assets
Fair Value		$ 1,255,870	$ 1,087,235
Total Unrealized Gains		363,476	230,781
Total Unrealized Losses		(669)	(7,237)
Amortized cost		691,000	635,000
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains		11,132	6,680	$ 21,830
Realized losses		(6,972)	(13,552)	(13,155)
Proceeds from the sale of securities		719,034	653,033	546,339
Fair value of fixed income securities, summarized by contractual maturities
Employee medical claims amount	$ 15,000
Equity securities
Nuclear decommissioning trust fund assets
Equity Securities		536,858	447,138
Total Unrealized Gains		337,681	222,147
Total Unrealized Losses		0	(459)
Fixed income securities
Nuclear decommissioning trust fund assets
Fair Value		716,137	637,356
Total Unrealized Gains		25,795	8,634
Total Unrealized Losses		(669)	(6,778)
Fair value of fixed income securities, summarized by contractual maturities
Less than one year		99,386
1 year - 5 years		299,410
5 years - 10 years		105,797
Greater than 10 years		211,544
Total		716,137
Other Receivables from Broker-Dealers and Clearing
Nuclear decommissioning trust fund assets
Fair Value		2,875	2,741
Total Unrealized Gains		0	0
Total Unrealized Losses		0	0
Nuclear Decommissioning Trusts
Nuclear decommissioning trust fund assets
Fair Value		1,010,775	851,134
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains		11,024	6,679	21,813
Realized losses		(6,972)	(13,552)	(13,146)
Proceeds from the sale of securities		473,806	554,385	542,246
Nuclear Decommissioning Trusts | Equity securities
Nuclear decommissioning trust fund assets
Equity Securities		529,716	402,008
Nuclear Decommissioning Trusts | Fixed income securities
Nuclear decommissioning trust fund assets
Fair Value		478,658	446,978
Fair value of fixed income securities, summarized by contractual maturities
Less than one year		26,984
1 year - 5 years		136,139
5 years - 10 years		105,797
Greater than 10 years		209,738
Total		478,658
Nuclear Decommissioning Trusts | Other Receivables from Broker-Dealers and Clearing
Nuclear decommissioning trust fund assets
Fair Value		2,401	2,148
Coal Reclamation Escrow Account | Fixed income securities
Fair value of fixed income securities, summarized by contractual maturities
Less than one year		31,953
1 year - 5 years		25,229
5 years - 10 years		0
Greater than 10 years		1,806
Total		58,988
Active Union Medical Trust | Fixed income securities
Fair value of fixed income securities, summarized by contractual maturities
Less than one year		40,449
1 year - 5 years		138,042
5 years - 10 years		0
Greater than 10 years		0
Total		178,491
Other Special Use Funds
Nuclear decommissioning trust fund assets
Fair Value		245,095	236,101
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains		108	1	17
Realized losses		0	0	(9)
Proceeds from the sale of securities		245,228	98,648	$ 4,093
Other Special Use Funds | Equity securities
Nuclear decommissioning trust fund assets
Equity Securities		7,142	45,130
Other Special Use Funds | Fixed income securities
Nuclear decommissioning trust fund assets
Fair Value		237,479	190,378
Other Special Use Funds | Other Receivables from Broker-Dealers and Clearing
Nuclear decommissioning trust fund assets
Fair Value		$ 474	$ 593