Regulatory Matters - Retail Rate Case Filing (Details)	Nov. 06, 2020 USD ($)	Oct. 31, 2019 USD ($) $ / kWh GW	Jun. 30, 2019 USD ($)	Aug. 13, 2018 USD ($)	Jan. 08, 2018 USD ($)	Mar. 27, 2017 USD ($) $ / kWh	Dec. 31, 2020 USD ($)	Dec. 04, 2020 USD ($)	Oct. 02, 2020 USD ($)
ACC
Public Utilities, General Disclosures [Line Items]
Revenue increase (decrease)	$ 169,000,000							$ 59,800,000	$ 89,700,000
Average annual customer bill increase (decrease), percent	5.14%							1.82%	2.70%
Recommended return on equity, percentage	10.00%								9.40%
Alternative, percentage									0.30%
Increment of fair value rate, percentage	0.80%								0.00%
Residential Utility Consumer Office
Public Utilities, General Disclosures [Line Items]
Revenue increase (decrease)								$ (50,100,000)	$ (20,800,000)
Average annual customer bill increase (decrease), percent								(1.52%)	(0.63%)
Recommended return on equity, percentage									8.74%
Increment of fair value rate, percentage									0.00%
ACC | APS
Public Utilities, General Disclosures [Line Items]
Proposed annual revenue increase		$ 184,000,000		$ (86,500,000)	$ (119,100,000)
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%
Approximate percentage of increase in average residential customer bill		5.40%				4.54%
Rate matter, cost base rate			$ 8,870,000,000
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
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
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
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
Coal Community Transition Plan | ACC
Public Utilities, General Disclosures [Line Items]
Amount funded by shareholders	$ 25,000,000						$ 25,000,000
Amount funded by customers, term	10 years
Amount funded by customers	$ 100,000,000
Coal Community Transition Plan | ACC | Navajo Nation, Economic Development Organization
Public Utilities, General Disclosures [Line Items]
Amount funded by shareholders	$ 1,250,000
Amount funded by shareholders, term	5 years
Coal Community Transition Plan | ACC | Navajo Nation, Electrification Projects
Public Utilities, General Disclosures [Line Items]
Amount funded by shareholders	$ 10,000,000
Amount funded by customers	10,000,000
Coal Community Transition Plan | ACC | Navajo Nation, Transmission Revenue Sharing
Public Utilities, General Disclosures [Line Items]
Amount funded by shareholders	$ 2,500,000
Coal Community Transition Plan | ACC | Navajo County Communities, Cholla Power Plant Closure
Public Utilities, General Disclosures [Line Items]
Amount funded by customers, term	5 years
Amount funded by customers	$ 12,000,000
Coal Community Transition Plan | ACC | Navajo Nation, Generation Station
Public Utilities, General Disclosures [Line Items]
Amount funded by customers	$ 3,700,000
Minimum | ACC | APS
Public Utilities, General Disclosures [Line Items]
Annual increase in retail base rates		$ 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