Commitments and Contingencies (Environmental Remediation) (Details) - SCE $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($) site
Jointly Owned Utility Plant Interests [Line Items]
Recorded estimated minimum liability	$ 278
Environmental remediation regulatory assets	265
Expected recovery from incentive mechanism	$ 39
Expected recovery from incentive mechanism (percent)	90.00%
Recovery through customer rates	$ 226
Recovery through customer rates (percent)	100.00%
Environmental remediation expense	$ 2
Clean up (period)	30 years
Expected remediation costs, low end of range	$ 13
Expected remediation costs, high end of range	$ 30
Material sites
Jointly Owned Utility Plant Interests [Line Items]
Identified remediation sites (number) | site	27
Minimum estimated liability	$ 1
Recorded estimated minimum liability	274
Cost may exceed liability	117
Material sites | San Onofre
Jointly Owned Utility Plant Interests [Line Items]
Recorded estimated minimum liability	$ 172
Immaterial sites
Jointly Owned Utility Plant Interests [Line Items]
Identified remediation sites (number) | site	15
Recorded estimated minimum liability	$ 4
Cost may exceed liability	$ 8