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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
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Nuclear decommissioning trust fund assets |  |  |
Fair Value | $ 1,564,027 | $ 1,420,641 |
Total Unrealized Gains | 358,112 | 337,994 |
Total Unrealized Losses | (40,868) | (69,091) |
Amortized cost | 1,120,000 | 927,000 |
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds |  |  |
Realized gains | 112,094 | 9,437 | $ 134,659
Realized losses | (41,780) | (40,239) | (8,438)
Proceeds from the sale of securities | 1,679,722 | 1,207,197 | 1,720,966
Nuclear Decommissioning Trusts |  |  |
Nuclear decommissioning trust fund assets |  |  |
Fair Value | 1,201,246 | 1,073,410 |
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds |  |  |
Realized gains | 111,922 | 9,017 | 134,610
Realized losses | (41,212) | (40,239) | (8,431)
Proceeds from the sale of securities | 1,324,978 | 979,639 | 1,457,305
Other Special Use Funds |  |  |
Nuclear decommissioning trust fund assets |  |  |
Fair Value | 362,781 | 347,231 |
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds |  |  |
Realized gains | 172 | 420 | 49
Realized losses | (568) | 0 | (7)
Proceeds from the sale of securities | 354,744 | 227,558 | $ 263,661
Equity securities |  |  |
Nuclear decommissioning trust fund assets |  |  |
Equity securities | 461,671 | 554,214 |
Total Unrealized Gains | 336,555 | 334,817 |
Total Unrealized Losses | 0 | (267) |
Equity securities | Nuclear Decommissioning Trusts |  |  |
Nuclear decommissioning trust fund assets |  |  |
Equity securities | 420,680 | 487,240 |
Equity securities | Other Special Use Funds |  |  |
Nuclear decommissioning trust fund assets |  |  |
Equity securities | 40,991 | 66,974 |
Available for sale-fixed income securities |  |  |
Nuclear decommissioning trust fund assets |  |  |
Fair Value | 1,100,927 | 861,637 |
Total Unrealized Gains | 21,518 | 3,177 |
Total Unrealized Losses | (40,868) | (68,795) |
Fair value of fixed income securities, summarized by contractual maturities |  |  |
Less than one year | 121,606 |  |
1 year – 5 years | 424,772 |  |
5 years – 10 years | 201,452 |  |
Greater than 10 years | 353,097 |  |
Total | 1,100,927 |  |
Available for sale-fixed income securities | Nuclear Decommissioning Trusts |  |  |
Nuclear decommissioning trust fund assets |  |  |
Fair Value | 781,333 | 582,343 |
Fair value of fixed income securities, summarized by contractual maturities |  |  |
Less than one year | 26,057 |  |
1 year – 5 years | 225,891 |  |
5 years – 10 years | 176,288 |  |
Greater than 10 years | 353,097 |  |
Total | 781,333 |  |
Available for sale-fixed income securities | Other Special Use Funds |  |  |
Nuclear decommissioning trust fund assets |  |  |
Fair Value | 319,594 | 279,294 |
Available for sale-fixed income securities | Coal Reclamation Escrow Account |  |  |
Fair value of fixed income securities, summarized by contractual maturities |  |  |
Less than one year | 58,692 |  |
1 year – 5 years | 46,120 |  |
5 years – 10 years | 0 |  |
Greater than 10 years | 0 |  |
Total | 104,812 |  |
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 | 36,857 |  |
1 year – 5 years | 152,761 |  |
5 years – 10 years | 25,164 |  |
Greater than 10 years | 0 |  |
Total | 214,782 |  |
Other |  |  |
Nuclear decommissioning trust fund assets |  |  |
Fair Value | 1,429 | 4,790 |
Total Unrealized Gains | 39 | 0 |
Total Unrealized Losses | 0 | (29) |
Other | Nuclear Decommissioning Trusts |  |  |
Nuclear decommissioning trust fund assets |  |  |
Fair Value | (767) | 3,827 |
Other | Other Special Use Funds |  |  |
Nuclear decommissioning trust fund assets |  |  |
Fair Value | $ 2,196 | $ 963 |

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