Summary of Significant Accounting Policies (Prepaid Insurance) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2019
Redeemable Noncontrolling Interest [Line Items]
Wildfire Insurance Fund contributions, noncurrent		$ 1,951	$ 2,155
Wildfire Insurance Fund contributions, current		204	204
Wildfire Insurance Fund contributions		$ 95	$ 95	$ 95
Measurement Input
Redeemable Noncontrolling Interest [Line Items]
Historical term used in estimate	10 years	9 years	8 years
Wildfire Insurance Fund
Redeemable Noncontrolling Interest [Line Items]
Wildfire Insurance Fund contributions, noncurrent		$ 2,000	$ 2,200
Wildfire Insurance Fund contributions, current		204	204
Wildfire Insurance Fund contributions					$ 2,400
Wildfire Insurance Fund liability, noncurrent		$ 450	$ 536
Insurance fund contribution amortization period	20 years	15 years	15 years
SCE
Redeemable Noncontrolling Interest [Line Items]
Wildfire Insurance Fund contributions, noncurrent		$ 1,951	$ 2,155
Wildfire Insurance Fund contributions, current		204	204
Wildfire Insurance Fund contributions		$ 95	$ 95	$ 95