Variable Interest Entities (Summary of Trusts' Income Statement) (Details) - SCE - VIE - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Trust II
Variable Interest Entity [Line Items]
Dividend income	$ 20	$ 20	$ 20
Dividend distributions	20	20	20
Trust III
Variable Interest Entity [Line Items]
Dividend income	16	16	16
Dividend distributions	16	16	16
Trust IV
Variable Interest Entity [Line Items]
Dividend income	17	17	17
Dividend distributions	17	17	17
Trust V
Variable Interest Entity [Line Items]
Dividend income	16	16	16
Dividend distributions	16	16	16
Trust VI
Variable Interest Entity [Line Items]
Dividend income	24	24	24
Dividend distributions	$ 24	$ 24	$ 24