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v3.19.3.a.u2

Summary of Significant Accounting Policies - Narrative (Details) $ / shares in Units, $ in Millions | 1 Months Ended | 12 Months Ended | 36 Months Ended
--- | --- | --- | ---
May 31, 2014 $ / kWh | Dec. 31, 2019 USD ($) $ / shares shares | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2019 USD ($) $ / shares shares
Approximate remaining average useful lives of utility property |  |  |  |  |
Depreciation |  | $ 522 | $ 486 | $ 453 |
Depreciation rates (as a percent) |  | 2.81% | 2.81% | 2.80% |
Allowance for Funds Used During Construction |  |  |  |  |
Composite rate used to calculate AFUDC (as a percent) |  | 6.98% | 7.03% | 6.68% |
Income Taxes |  |  |  |  |
Percent likelihood largest tax benefit amount is realized (greater than) |  | 50.00% |  |  |
Intangible Assets |  |  |  |  |
Amortization expense |  | $ 66 | $ 68 | $ 72 |
Estimated amortization expense on existing intangible assets over the next five years |  |  |  |  |
2019 |  | 68 |  |  | $ 68
2020 |  | 52 |  |  | 52
2021 |  | 41 |  |  | 41
2022 |  | 32 |  |  | 32
2023 |  | $ 22 |  |  | $ 22
Remaining amortization period for intangible assets |  | 8 years |  |  |
Pinnacle West |  |  |  |  |
Preferred Stock |  |  |  |  |
Preferred stock, shares authorized (in shares) | shares |  | 10,000,000 |  |  | 10,000,000
ARIZONA PUBLIC SERVICE COMPANY |  |  |  |  |
Nuclear Fuel |  |  |  |  |
Charges for the permanent disposal of spent nuclear fuel (in dollars per kWh) | $ / kWh | 0.001 |  |  |  |
Preferred Stock |  |  |  |  |
Preferred stock, shares authorized (in shares) | shares |  | 15,535,000 |  |  | 15,535,000
Preferred stock par or stated value per share 1 (in dollars per share) | $ / shares |  | $ 25 |  |  | $ 25
Preferred stock par or stated value per share 2 (in dollars per share) | $ / shares |  | 50 |  |  | 50
Preferred stock par or stated value per share 3 (in dollars per share) | $ / shares |  | $ 100 |  |  | $ 100
Minimum |  |  |  |  |
Approximate remaining average useful lives of utility property |  |  |  |  |
Depreciation rates (as a percent) |  |  |  |  | 0.18%
Maximum |  |  |  |  |
Approximate remaining average useful lives of utility property |  |  |  |  |
Depreciation rates (as a percent) |  |  |  |  | 24.49%
Investments |  |  |  |  |
Ownership percentage for classification as cost method investments by El Dorado |  | 20.00% |  |  |
Fossil Plant |  |  |  |  |
Approximate remaining average useful lives of utility property |  |  |  |  |
Average useful life |  | 17 years |  |  |
Nuclear plant |  |  |  |  |
Approximate remaining average useful lives of utility property |  |  |  |  |
Average useful life |  | 22 years |  |  |
Other Generation |  |  |  |  |
Approximate remaining average useful lives of utility property |  |  |  |  |
Average useful life |  | 21 years |  |  |
Transmission |  |  |  |  |
Approximate remaining average useful lives of utility property |  |  |  |  |
Average useful life |  | 40 years |  |  |
Distribution |  |  |  |  |
Approximate remaining average useful lives of utility property |  |  |  |  |
Average useful life |  | 34 years |  |  |
General plant |  |  |  |  |
Approximate remaining average useful lives of utility property |  |  |  |  |
Average useful life |  | 8 years |  |  |
El Paso's Interest in Four Corners | 4CA |  |  |  |  |
Utility Plant and Depreciation [Line Items] |  |  |  |  |
Ownership interest acquired (as a percent) |  | 7.00% |  |  | 7.00%

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