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Investments in Nuclear Decommissioning Trusts and Other Special Use Funds (Details) - APS - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022 | Dec. 31, 2022
Nuclear decommissioning trust fund assets |  |  |  |  |
Fair Value | $ 1,514,395 |  | $ 1,514,395 |  | $ 1,420,641
Total Unrealized Gains |  |  | 381,803 |  | 337,994
Total Unrealized Losses |  |  | (58,187) |  | (69,091)
Amortized cost | 1,028,000 |  | 1,028,000 |  | 927,000
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds |  |  |  |  |
Realized gains | 35,231 | $ 6,282 | 36,441 | $ 7,305 |
Realized losses | (11,192) | (12,439) | (16,886) | (19,674) |
Proceeds from the sale of securities | 340,902 | 330,432 | 567,528 | 691,670 |
Nuclear Decommissioning Trusts |  |  |  |  |
Nuclear decommissioning trust fund assets |  |  |  |  |
Fair Value | 1,162,397 |  | 1,162,397 |  | 1,073,410
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds |  |  |  |  |
Realized gains | 35,231 | 6,282 | 36,441 | 7,305 |
Realized losses | (11,192) | (12,439) | (16,886) | (19,674) |
Proceeds from the sale of securities | 298,761 | 309,966 | 434,946 | 629,659 |
Other Special Use Funds |  |  |  |  |
Nuclear decommissioning trust fund assets |  |  |  |  |
Fair Value | 351,998 |  | 351,998 |  | 347,231
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds |  |  |  |  |
Realized gains | 0 | 0 | 0 | 0 |
Realized losses | 0 | 0 | 0 | 0 |
Proceeds from the sale of securities | 42,141 | $ 20,466 | 132,582 | $ 62,011 |
Equity securities |  |  |  |  |
Nuclear decommissioning trust fund assets |  |  |  |  |
Equity securities | 546,349 |  | 546,349 |  | 554,214
Total Unrealized Gains |  |  | 378,973 |  | 334,817
Total Unrealized Losses |  |  | (5) |  | (267)
Equity securities | Nuclear Decommissioning Trusts |  |  |  |  |
Nuclear decommissioning trust fund assets |  |  |  |  |
Equity securities | 519,099 |  | 519,099 |  | 487,240
Equity securities | Other Special Use Funds |  |  |  |  |
Nuclear decommissioning trust fund assets |  |  |  |  |
Equity securities | 27,250 |  | 27,250 |  | 66,974
Available for sale-fixed income securities |  |  |  |  |
Nuclear decommissioning trust fund assets |  |  |  |  |
Fair Value | 972,774 |  | 972,774 |  | 861,637
Total Unrealized Gains |  |  | 2,830 |  | 3,177
Total Unrealized Losses |  |  | (58,178) |  | (68,795)
Fair value of fixed income securities, summarized by contractual maturities |  |  |  |  |
Less than one year | 114,971 |  | 114,971 |  |
1 year – 5 years | 355,424 |  | 355,424 |  |
5 years – 10 years | 201,939 |  | 201,939 |  |
Greater than 10 years | 300,440 |  | 300,440 |  |
Total | 972,774 |  | 972,774 |  |
Available for sale-fixed income securities | Nuclear Decommissioning Trusts |  |  |  |  |
Nuclear decommissioning trust fund assets |  |  |  |  |
Fair Value | 649,545 |  | 649,545 |  | 582,343
Fair value of fixed income securities, summarized by contractual maturities |  |  |  |  |
Less than one year | 19,020 |  | 19,020 |  |
1 year – 5 years | 175,774 |  | 175,774 |  |
5 years – 10 years | 158,261 |  | 158,261 |  |
Greater than 10 years | 296,490 |  | 296,490 |  |
Total | 649,545 |  | 649,545 |  |
Available for sale-fixed income securities | Other Special Use Funds |  |  |  |  |
Nuclear decommissioning trust fund assets |  |  |  |  |
Fair Value | 323,229 |  | 323,229 |  | 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 | 57,267 |  | 57,267 |  |
1 year – 5 years | 35,020 |  | 35,020 |  |
5 years – 10 years | 0 |  | 0 |  |
Greater than 10 years | 3,950 |  | 3,950 |  |
Total | 96,237 |  | 96,237 |  |
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 | 38,684 |  | 38,684 |  |
1 year – 5 years | 144,630 |  | 144,630 |  |
5 years – 10 years | 43,678 |  | 43,678 |  |
Greater than 10 years | 0 |  | 0 |  |
Total | 226,992 |  | 226,992 |  |
Other |  |  |  |  |
Nuclear decommissioning trust fund assets |  |  |  |  |
Fair Value | (4,728) |  | (4,728) |  | 4,790
Total Unrealized Gains |  |  | 0 |  | 0
Total Unrealized Losses |  |  | (4) |  | (29)
Other | Nuclear Decommissioning Trusts |  |  |  |  |
Nuclear decommissioning trust fund assets |  |  |  |  |
Fair Value | (6,247) |  | (6,247) |  | 3,827
Other | Other Special Use Funds |  |  |  |  |
Nuclear decommissioning trust fund assets |  |  |  |  |
Fair Value | $ 1,519 |  | $ 1,519 |  | $ 963

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