Regulatory Matters - Four Corners and Cholla (Details) - APS $ in Millions			9 Months Ended
	Dec. 23, 2014 USD ($)	Dec. 30, 2013 USD ($) MW	Sep. 30, 2015 USD ($)
SCE | Four Corners Units 4 and 5
Business Acquisition [Line Items]
Ownership interest acquired		48.00%
Settlement agreement, ACC approved rate adjustment, annualized customer impact	$ 57.1
Net receipt due to negotiation of alternate arrangement		$ 40.0
Capacity rights over the Arizona Transmission System assign to third-parties | MW		1,555
Capacity rights related to marketing and trading group for transmission of the additional power received assign to third-parties | MW		300
Four Corners cost deferral | SCE | Four Corners Units 4 and 5
Business Acquisition [Line Items]
Regulatory assets, non-current			$ 72.0
Regulatory noncurrent asset amortization period			10 years
Retired power plant costs
Business Acquisition [Line Items]
Net book value			$ 124.0