Regulatory Matters - Retail Rate Case Filing (Details)	Aug. 02, 2021 USD ($)	Nov. 06, 2020 USD ($)	Oct. 02, 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 ($)	Dec. 04, 2020 USD ($)
ACC
Public Utilities, General Disclosures [Line Items]
Revenue increase (decrease)		$ 169,000,000	$ 89,700,000							$ 59,800,000
Average annual customer bill increase (decrease), percent		5.14%	2.70%							1.82%
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)			$ (20,800,000)							$ (50,100,000)
Average annual customer bill increase (decrease), percent			(0.63%)							(1.52%)
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
Expenses from recovery of deferral and rate base effects			$ 110,000,000
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
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
Retail Rate Case Filing with Arizona Corporation Commission | ACC | APS | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Revenue increase (decrease)	$ (111,000,000)
Recommended return on equity, percentage	9.16%
Increment of fair value rate, percentage	0.15%
Reduction on equity percentage	0.10%
Effective fair value percentage	0.05%
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 customers		$ 100,000,000
Amount funded by customers, term		10 years
Amount funded by shareholders		$ 25,000,000							$ 25,000,000
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 customers		$ 10,000,000
Amount funded by shareholders		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		$ 12,000,000
Amount funded by customers, term		5 years
Coal Community Transition Plan | ACC | Navajo Nation, Generation Station
Public Utilities, General Disclosures [Line Items]
Amount funded by customers		$ 3,700,000
Coal Community Transition Plan | Retail Rate Case Filing with Arizona Corporation Commission | ACC | APS | Navajo Nation, Economic Development Organization | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Disallowance of annual amortization percentage	15.00%
Amount funded by customers	$ 50,000,000
Amount funded by customers, term	10 years
Coal Community Transition Plan | Retail Rate Case Filing with Arizona Corporation Commission | ACC | APS | Navajo County Communities, Cholla Power Plant Closure | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Amount funded by shareholders	$ 5,000,000
Amount funded by shareholders, term	5 years
Coal Community Transition Plan | Retail Rate Case Filing with Arizona Corporation Commission | ACC | APS | Navajo Nation, Hopi Tribe | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Amount funded by shareholders	$ 1,675,000
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