Variable Interest Entities (Trusts) (Details) - SCE	3 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($) MW	Mar. 31, 2020 USD ($) MW	Dec. 31, 2017 USD ($) $ / shares	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2020 USD ($)
Variable Interest Entity [Line Items]
Common stock	$ 2,168,000,000							$ 2,168,000,000
Trust Securities [Member]
Variable Interest Entity [Line Items]
Liquidation value (in dollars per share) | $ / shares			$ 2,500
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Liquidation value (in dollars per share) | $ / shares			$ 25
Common stock	$ 10,000		$ 10,000					10,000
SCE Power Purchase Contracts
Variable Interest Entity [Line Items]
Power generating capacity for majority interest (in megawatts) | MW	3,916	4,996
Amount of related party transaction	$ 159,000,000	$ 151,000,000
Trust II
Variable Interest Entity [Line Items]
Liquidation preference							$ 400,000,000
Trust II | Trust Securities [Member]
Variable Interest Entity [Line Items]
Liquidation preference	220,000,000							220,000,000
Trust II | 5.10% Series G (cumulative)
Variable Interest Entity [Line Items]
Security dividend rate, (as a percent)							5.10%
Liquidation preference	220,000,000						$ 400,000,000	220,000,000
Trust III
Variable Interest Entity [Line Items]
Liquidation preference						$ 275,000,000
Trust III | Trust Securities [Member]
Variable Interest Entity [Line Items]
Liquidation preference	275,000,000							275,000,000
Trust III | 5.75% Series H (cumulative)
Variable Interest Entity [Line Items]
Security dividend rate, (as a percent)						5.75%
Liquidation preference	275,000,000					$ 275,000,000		275,000,000
Trust IV
Variable Interest Entity [Line Items]
Liquidation preference					$ 325,000,000
Trust IV | Trust Securities [Member]
Variable Interest Entity [Line Items]
Liquidation preference	325,000,000							325,000,000
Trust IV | 5.375% Series J (cumulative)
Variable Interest Entity [Line Items]
Security dividend rate, (as a percent)					5.375%
Liquidation preference	325,000,000				$ 325,000,000			325,000,000
Trust V
Variable Interest Entity [Line Items]
Liquidation preference				$ 300,000,000
Trust V | Trust Securities [Member]
Variable Interest Entity [Line Items]
Liquidation preference	300,000,000							300,000,000
Trust V | 5.45% Series K (cumulative)
Variable Interest Entity [Line Items]
Security dividend rate, (as a percent)				5.45%
Liquidation preference	300,000,000			$ 300,000,000				300,000,000
Trust VI
Variable Interest Entity [Line Items]
Liquidation preference			$ 475,000,000
Trust VI | Trust Securities [Member]
Variable Interest Entity [Line Items]
Liquidation preference	475,000,000							475,000,000
Trust VI | 5.00% Series L (cumulative)
Variable Interest Entity [Line Items]
Security dividend rate, (as a percent)			5.00%
Liquidation preference	$ 475,000,000		$ 475,000,000					$ 475,000,000