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Retirement Plans and Other Postretirement Benefits - Fair Value of Pinnacle West's Pension Plan (Details) - USD ($) $ in Thousands | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
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Pension Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | $ 530,171 | $ 691,233 |
Fair value of plan assets | 3,812,041 | 3,886,544 | $ 3,318,351
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 | 1,350,751 | 1,398,305 |
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 | 1,931,119 | 1,797,006 |
Other Benefits |  |  |
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category |  |  |
Other | 126,552 | 118,440 |
Fair value of plan assets | 872,435 | 961,165 | $ 837,494
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 | 491,981 | 612,921 |
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 | 253,902 | 229,804 |
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 | 0 |
Fair value of plan assets | 821 | 9,911 |
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 | 821 | 9,911 |
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 | 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 | 0 |
Fair value of plan assets | 121 | 1,909 |
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 | 121 | 1,909 |
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 | 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 | 1,765,623 | 1,684,782 |
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 | 1,765,623 | 1,684,782 |
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 | 244,572 | 221,488 |
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 | 244,572 | 221,488 |
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 | 1,008,211 | 794,571 |
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 | 1,008,211 | 794,571 |
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 | 287,057 | 258,102 |
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 | 287,057 | 258,102 |
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 | 165,496 | 112,224 |
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 | 165,496 | 112,224 |
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 | 9,330 | 8,316 |
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 | 9,330 | 8,316 |
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 | 209,063 | 331,058 |
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 | 209,063 | 331,058 |
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 | 176,024 | 175,605 |
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 | 176,024 | 175,605 |
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 | 132,656 | 262,765 |
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 | 132,656 | 262,765 |
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 | 26,262 | 34,310 |
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 | 26,262 | 34,310 |
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 | 255,141 | 407,522 |
Fair value of plan assets | 255,141 | 407,522 |
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 | 96,547 | 94,674 |
Fair value of plan assets | 96,547 | 94,674 |
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 | 173,197 | 191,595 |
Fair value of plan assets | 173,197 | 191,595 |
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 | 23,851 | 19,778 |
Fair value of plan assets | 23,851 | 19,778 |
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 | 15,730 | 22,420 |
Fair value of plan assets | 15,730 | 22,420 |
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 | 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 | 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 | 86,103 | 69,696 |
Fair value of plan assets | 86,103 | 69,696 |
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 | 6,154 | 3,988 |
Fair value of plan assets | 8,671 | 146,983 |
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 | 2,517 | 142,995 |
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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