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Retirement Plans and Other Benefits Retirement Plans and Other Benefits - Additional Information (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items] |  |  |
Partnership funding commitments, contribution amount (up to) | $ 50,000,000 |  |
Partnership funding commitments, funded amount | $ 38,000,000 |  |
Pension Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Funded percentage (more than) | 100.00% |  |
Expected long-term return on plan assets for next fiscal year (as a percent) | 5.75% |  |
Contributions |  |  |
Employer contributions | $ 150,000,000 | $ 50,000,000 | $ 100,000,000
Minimum contributions under MAP-21 |  |  |
Minimum contributions under MAP-21 | 0 |  |
Voluntary employer contributions over next three years (up to) | $ 100,000,000 |  |
Other Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Expected long-term return on plan assets for next fiscal year (as a percent) | 5.00% |  |
Contributions |  |  |
Employer contributions | $ 0 | 0 |
Minimum contributions under MAP-21 |  |  |
Retiree medical cost reimbursement | 30,000,000 | 72,000,000 |
Pinnacle West |  |  |
Employee savings plan benefits |  |  |
Expenses recorded for the defined contribution savings plan | $ 11,000,000 | $ 11,000,000 | 10,000,000
ARIZONA PUBLIC SERVICE COMPANY |  |  |
Employee savings plan benefits |  |  |
APS's employees share of total cost of the plans (as a percent) | 99.00% |  |
ARIZONA PUBLIC SERVICE COMPANY | Other Benefits |  |  |
Contributions |  |  |
Employer contributions |  |  | $ 1,000,000

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- Definition An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation during next fiscal year. + References No definition available. + Details
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