Regulatory Matters - Four Corners, Cholla and Navajo Plant (Details) - ARIZONA PUBLIC SERVICE COMPANY - USD ($) $ in Millions			1 Months Ended		3 Months Ended	12 Months Ended
	Dec. 23, 2014	Dec. 30, 2013	Sep. 30, 2018	Apr. 30, 2018	Jun. 30, 2016	Dec. 31, 2018	Dec. 31, 2015
Retired power plant costs
Acquisition
Regulatory asset, net book value						$ 89.0
Navajo Plant
Acquisition
Regulatory asset, net book value						88.0
SCE | Four Corners
Acquisition
Regulatory assets							$ 12.0
Regulatory assets, write of amount					$ 12.0
Four Corners Units 4 and 5 | SCE
Acquisition
Ownership interest acquired (as a percent)		48.00%
Settlement agreement, ACC approved rate adjustment, annualized customer impact	$ 57.1		$ 58.5	$ 67.5
Transmission termination agreement net receipt due to negotiation of alternate arrangement		$ 40.0
Four Corners Units 4 and 5 | SCE | Four Corners cost deferral
Acquisition
Regulatory assets						$ 48.0
Amortization period						10 years