Revenue (Summary of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Total operating revenue	$ 2,564	$ 2,463
Southern California Edison
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2,728
Alternative revenue programs and other operating revenue	(174)
Total operating revenue	2,554	2,456
Southern California Edison | Earning Activities
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,536
Alternative revenue programs and other operating revenue	(23)
Total operating revenue	1,513	1,552
Southern California Edison | Cost- Recovery Activities
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,192
Alternative revenue programs and other operating revenue	(151)
Total operating revenue	$ 1,041	$ 904