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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
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%