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Retirement Plans and Other Benefits Retirement Plans and Other Benefits (Details) | 1 Months Ended | 12 Months Ended |
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Jul. 31, 2012 | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($) | Dec. 31, 2012 USD ($) | Dec. 31, 2011 USD ($) | Jan. 01, 2015 Age
Plan Design Changes [Abstract] |  |  |  |  |  |  |  |  |
Amount of other postretirement benefit trust assets for union employee medical costs |  | $ 186,000,000 |  |  |  |  |  |  |
Amount of pension and other postretirement benefit costs deferred |  |  |  |  |  |  | $ 14,000,000 | $ 11,000,000 |
Regulatory asset amortization period | 3 years |  |  |  |  |  |  |  |
Amortization of regulatory assets |  |  |  | $ 5,000,000 | $ 8,000,000 | $ 8,000,000 | $ 4,000,000 |  |
Partnership funding commitments, contribution amount (up to) |  | 75,000,000 |  |  |  |  |  |  |
Partnership funding commitments, funded amount |  | $ 58,000,000 |  |  |  |  |  |  |
Pension Benefits |  |  |  |  |  |  |  |  |
Plan Design Changes [Abstract] |  |  |  |  |  |  |  |  |
Expected long-term return on plan assets for next fiscal year (as a percent) |  | 6.05% |  |  |  |  |  |  |
Contributions |  |  |  |  |  |  |  |  |
Employer's contributions under the plan |  | $ 100,000,000 | $ 100,000,000 | 100,000,000 |  |  |  |  |
Minimum contributions under MAP-21 |  |  |  |  |  |  |  |  |
Minimum contributions under MAP-21 |  | 0 |  |  |  |  |  |  |
Voluntary employer contributions over next three years (up to) |  | $ 250,000,000 |  |  |  |  |  |  |
Other Benefits |  |  |  |  |  |  |  |  |
Plan Design Changes [Abstract] |  |  |  |  |  |  |  |  |
Age eligible for benefit | Age |  |  |  |  |  |  |  |  | 65
Effect of plan amendment on accumulated benefit obligation |  |  |  | 316,000,000 |  |  |  |  |
Expected long-term return on plan assets for next fiscal year (as a percent) |  | 5.55% |  |  |  |  |  |  |
Contributions |  |  |  |  |  |  |  |  |
Employer's contributions under the plan |  | $ 353,000 | 819,000 | 1,000,000 |  |  |  |  |
Pinnacle West |  |  |  |  |  |  |  |  |
Employee savings plan benefits |  |  |  |  |  |  |  |  |
Expenses recorded for the defined contribution savings plan |  | $ 10,000,000 | 10,000,000 | 9,000,000 |  |  |  |  |
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 | Pension Benefits |  |  |  |  |  |  |  |  |
Contributions |  |  |  |  |  |  |  |  |
Employer's contributions under the plan |  | $ 100,000,000 | 100,000,000 | 100,000,000 |  |  |  |  |
ARIZONA PUBLIC SERVICE COMPANY | Other Benefits |  |  |  |  |  |  |  |  |
Contributions |  |  |  |  |  |  |  |  |
Employer's contributions under the plan |  | $ 1,000,000 | $ 1,000,000 | $ 1,000,000 |  |  |  |  |

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- Definition Defined Benefit Plan - Amount of Other Postretirement Benefit Trust Assets for Union Employee Medical Costs + References No definition available. + Details
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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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