Commitments and Contingencies (Environmental Remediation) (Details) - SCE $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2019 USD ($) site	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Jointly Owned Utility Plant Interests [Line Items]
Recorded estimated minimum liability		$ 242
Environmental remediation regulatory assets		237
Expected recovery from incentive mechanism		$ 41
Expected recovery from incentive mechanism (percent)		90.00%
Recovery through customer rates		$ 196
Recovery through customer rates (percent)		100.00%
Cost may exceed recorded liability, material sites		$ 91
Cost may exceed recorded liability, immaterial sites		$ 7
Clean up (period)		30 years
Remediation cost estimates (period)	5 years
Expected remediation costs for each of the next four years, low end of range		$ 5
Expected remediation costs for each of the next four years, high end of range		15
Environmental remediation expense		$ 9	$ 8	$ 9
Material sites
Jointly Owned Utility Plant Interests [Line Items]
Identified material sites (number) | site		22
Minimum estimated liability		$ 1
Recorded estimated minimum liability		238
Material sites | San Onofre
Jointly Owned Utility Plant Interests [Line Items]
Recorded estimated minimum liability		$ 177
Immaterial sites
Jointly Owned Utility Plant Interests [Line Items]
Immaterial sites (number) | site		15
Immaterial sites | Minimum
Jointly Owned Utility Plant Interests [Line Items]
Recorded estimated minimum liability		$ 4