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Regulatory Matters - Retail Rate Case Filing (Details) | Oct. 31, 2019 USD ($) $ / kWh GW | Jun. 30, 2019 USD ($) | Mar. 27, 2017 USD ($) $ / kWh | Oct. 02, 2020 USD ($)
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Retail Rate Case Filing with Arizona Corporation Commission | ACC | APS |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |
Base rate decrease, elimination of tax expense adjustment mechanism | $ 115,000,000 |  |  |
Approximate percentage of increase in average customer bill | 5.60% |  | 3.28% |
Rate matter, cost base rate |  | $ 8,870,000,000 |  |
Net retail base rate, increase |  |  | $ 94,600,000 |
Non-fuel and non-depreciation base rate, increase |  |  | 87,200,000 |
Fuel-related base rate decrease |  |  | 53,600,000 |
Base rate increase, changes in depreciation schedules |  |  | $ 61,000,000.0 |
Approximate percentage of increase in average residential customer bill | 5.40% |  | 4.54% |
Authorized return on common equity (as a percent) |  |  | 10.00% |
Percentage of debt in capital structure |  |  | 44.20% |
Percentage of common equity in capital structure |  |  | 55.80% |
Rate matter, resource comparison proxy for exported energy (in dollars per kWh) | $ / kWh |  |  | 0.129 |
Base fuel rate (in dollars per kWh) | $ / kWh | 0.030168 |  |  |
Funding limited income crisis bill program | $ 1,250,000 |  |  |
Commercial customers, market pricing, threshold | GW | 0.02 |  |  |
AZ Sun Program Phase 2 | Retail Rate Case Filing with Arizona Corporation Commission | ACC | APS |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |
Public utilities, minimum annual renewable energy standard and tariff |  |  | $ 10,000,000 |
Public utilities, maximum annual renewable energy standard and tariff |  |  | $ 15,000,000 |
Minimum | ACC | APS |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |
Operating Results | $ 69,000,000 |  |  |
Minimum | Retail Rate Case Filing with Arizona Corporation Commission | ACC | APS |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |
Rate matter, environmental surcharge cap rate (in dollars per kWh) | $ / kWh |  |  | 0.00016 |
Maximum | Retail Rate Case Filing with Arizona Corporation Commission | ACC | APS |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |
Rate matter, environmental surcharge cap rate (in dollars per kWh) | $ / kWh |  |  | 0.00050 |
Subsequent Event | ACC |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |
Revenue increase (decrease) |  |  |  | $ 89,700,000
Recommended return on equity, percentage |  |  |  | 9.40%
Increment of fair value rate, percentage |  |  |  | 0.00%
Alternative, percentage |  |  |  | 0.30%
Average annual customer bill increase (decrease), percent |  |  |  | 2.70%
Subsequent Event | Residential Utility Consumer Office |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |
Revenue increase (decrease) |  |  |  | $ (20,800,000)
Recommended return on equity, percentage |  |  |  | 8.74%
Increment of fair value rate, percentage |  |  |  | 0.00%
Average annual customer bill increase (decrease), percent |  |  |  | (0.63%)

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