Regulatory Matters - Four Corners and Cholla (Details) - APS - USD ($) $ in Millions	1 Months Ended
	Sep. 30, 2018	Apr. 30, 2018	Sep. 30, 2020
SCE | Four Corners Units 4 and 5
Business Acquisition [Line Items]
Settlement agreement, ACC approved rate adjustment, annualized customer impact	$ 58.5	$ 67.5
Retired power plant costs
Business Acquisition [Line Items]
Net book value			$ 61.0
Navajo Plant
Business Acquisition [Line Items]
Net book value			$ 74.0