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Retirement Plans and Other Postretirement Benefits - Fair Value of Pinnacle West's Pension Plan (Details) - USD ($) $ in Thousands | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
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Pension Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | $ 399,298 | $ 429,391 |
Fair value of plan assets | 2,835,549 | 2,829,485 | $ 3,812,041
Pension Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 885,721 | 893,285 |
Pension Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 1,550,530 | 1,506,809 |
Other Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | 107,201 | 106,356 |
Fair value of plan assets | 696,494 | 652,287 | $ 872,435
Other Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 391,019 | 371,731 |
Other Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 198,274 | 174,200 |
Cash and cash equivalents | Pension Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other |  | 0 |
Fair value of plan assets |  | 1,252 |
Cash and cash equivalents | Pension Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets |  | 1,252 |
Cash and cash equivalents | Pension Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets |  | 0 |
Cash and cash equivalents | Other Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other |  | 0 |
Fair value of plan assets |  | 204 |
Cash and cash equivalents | Other Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets |  | 204 |
Cash and cash equivalents | Other Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets |  | 0 |
Corporate | Pension Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | 0 | 0 |
Fair value of plan assets | 1,415,346 | 1,374,810 |
Corporate | Pension Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Corporate | Pension Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 1,415,346 | 1,374,810 |
Corporate | Other Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | 0 | 0 |
Fair value of plan assets | 189,902 | 166,879 |
Corporate | Other Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Corporate | Other Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 189,902 | 166,879 |
U.S. Treasury | Pension Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | 0 | 0 |
Fair value of plan assets | 622,273 | 635,245 |
U.S. Treasury | Pension Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 622,273 | 635,245 |
U.S. Treasury | Pension Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
U.S. Treasury | Other Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | 0 | 0 |
Fair value of plan assets | 207,665 | 221,936 |
U.S. Treasury | Other Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 207,665 | 221,936 |
U.S. Treasury | Other Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Other fixed income | Pension Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | 0 | 0 |
Fair value of plan assets | 135,184 | 131,999 |
Other fixed income | Pension Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Other fixed income | Pension Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 135,184 | 131,999 |
Other fixed income | Other Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | 0 | 0 |
Fair value of plan assets | 8,372 | 7,321 |
Other fixed income | Other Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Other fixed income | Other Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 8,372 | 7,321 |
Common stock equities | Pension Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | 0 | 0 |
Fair value of plan assets | 150,657 | 155,231 |
Common stock equities | Pension Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 150,657 | 155,231 |
Common stock equities | Pension Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Common stock equities | Other Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | 0 | 0 |
Fair value of plan assets | 139,952 | 127,493 |
Common stock equities | Other Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 139,952 | 127,493 |
Common stock equities | Other Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Mutual funds | Pension Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | 0 | 0 |
Fair value of plan assets | 112,791 | 101,557 |
Mutual funds | Pension Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 112,791 | 101,557 |
Mutual funds | Pension Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Mutual funds | Other Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | 0 | 0 |
Fair value of plan assets | 22,256 | 18,824 |
Mutual funds | Other Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 22,256 | 18,824 |
Mutual funds | Other Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Equities | Pension Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | 192,945 | 181,912 |
Fair value of plan assets | 192,945 | 181,912 |
Equities | Pension Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Equities | Pension Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Equities | Other Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | 81,724 | 73,956 |
Fair value of plan assets | 81,724 | 73,956 |
Equities | Other Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Equities | Other Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Real estate | Pension Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | 140,613 | 174,228 |
Fair value of plan assets | 140,613 | 174,228 |
Real estate | Pension Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Real estate | Pension Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Real estate | Other Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | 20,001 | 23,541 |
Fair value of plan assets | 20,001 | 23,541 |
Real estate | Other Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Real estate | Other Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Partnerships | Pension Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other |  | 13,359 |
Fair value of plan assets |  | 13,359 |
Partnerships | Pension Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets |  | 0 |
Partnerships | Pension Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets |  | 0 |
Short-term investments and other | Pension Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | 65,740 | 59,892 |
Fair value of plan assets | 65,740 | 59,892 |
Short-term investments and other | Pension Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Short-term investments and other | Pension Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 0 | 0 |
Short-term investments and other | Other Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | 5,476 | 8,859 |
Fair value of plan assets | 26,622 | 12,133 |
Short-term investments and other | Other Benefits | Level 1 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | 21,146 | 3,274 |
Short-term investments and other | Other Benefits | Level 2 |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Gross fair value of plan assets | $ 0 | $ 0 |

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