Regulatory Matters - COVID-19 (Details) - APS - USD ($)		1 Months Ended
	Jan. 21, 2021	Mar. 31, 2021	Dec. 31, 2020	May 05, 2020
Public Utilities, General Disclosures [Line Items]
Percentage increase under PSA effective for first billing cycle beginning April 2021		50.00%
Remaining percentage increase under PSA effective for first billing cycle beginning November 2021		50.00%
Demand side management funds				$ 36,000,000
Customer credits		$ 43,000,000
Customer credits, additional funds		$ 7,000,000
Voluntary funds			$ 15,000,000
Customer COVID assistance			12,400,000
Non-customer funds			8,800,000
Bill credits for limited income customers			$ 3,600,000
Threshold percentage for deferral of potential recovery			50.00%
Threshold for deferral of potential recovery			$ 2,500,000
Customer support fund, bill credit			100
Expanded credit for limited income customers			300
Customer assistance, small customers, bill credit			1,000
Additional bill credit for delinquent limited income customers			250
Customer support fund, non-profits and community organizations			$ 2,700,000
Damage from Fire, Explosion or Other Hazard
Public Utilities, General Disclosures [Line Items]
Customer support fund, payment period	8 months
Past due balance threshold qualifying for payment extension	$ 75