Regulatory Matters - Four Corners and Cholla (Details) $ in Millions			1 Months Ended	12 Months Ended
	Dec. 23, 2014 USD ($)	Dec. 30, 2013 USD ($) MW	Jul. 31, 2012	Dec. 31, 2015 USD ($)
Acquisition
Regulatory asset amortization period			3 years
Retired power plant costs | APS
Acquisition
Regulatory asset, net book value				$ 122.0
SCE | Four Corners | APS
Acquisition
Regulatory assets				12.0
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 Units 4 and 5 | SCE | APS
Acquisition
Ownership interest acquired		48.00%
Settlement agreement, ACC approved rate adjustment, annualized customer impact	$ 57.1
Four Corners Units 4 and 5 | SCE | Four Corners cost deferral | APS
Acquisition
Regulatory assets				$ 70.0
Regulatory asset amortization period				10 years