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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 |

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