Regulatory Matters - Retail Rate Case Filing (Details) - ACC - APS	Oct. 31, 2019 USD ($) GW	Jun. 30, 2019 USD ($)	Mar. 27, 2017 USD ($) $ / kWh
Retail Rate Case Filing with Arizona Corporation Commission
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
Funding limited income crisis bill program	$ 1,250,000
Commercial customers, market pricing, threshold | GW	0.2
AZ Sun Program Phase 2 | Retail Rate Case Filing with Arizona Corporation Commission
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
Public Utilities, General Disclosures [Line Items]
Operating Results	$ 69,000,000
Minimum | Retail Rate Case Filing with Arizona Corporation Commission
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
Public Utilities, General Disclosures [Line Items]
Rate matter, environmental surcharge cap rate (in dollars per kWh) | $ / kWh			0.00050