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Regulatory Matters - Retail Rate Case Filing (Details) - Retail Rate Case Filing with Arizona Corporation Commission - ACC - APS - USD ($) $ in Millions | Mar. 27, 2017 | Jun. 01, 2016 | Dec. 31, 2015 | Jun. 01, 2011
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Public Utilities, General Disclosures [Line Items] |  |  |  |
Net retail rate increase |  | $ 165.9 |  | $ 95.5
Adjustor account balance transferred into base rates, amount |  |  | $ 267.6 |
Approximate percentage of increase in average customer bill | 3.28% | 5.74% |  |
Approximate percentage of increase in average residential customer bill | 4.54% | 7.96% |  |

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