Variable Interest Entities (Summary of Trusts' Income Statement) (Details) - Variable Interest Entity, Not Primary Beneficiary - Southern California Edison - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Trust I
Variable Interest Entity
Dividend income	$ 6	$ 6	$ 13	$ 13
Dividend distributions	6	6	13	13
Trust II
Variable Interest Entity
Dividend income	5	5	10	10
Dividend distributions	5	5	10	10
Trust III
Variable Interest Entity
Dividend income	4	4	8	8
Dividend distributions	4	4	8	8
Trust IV
Variable Interest Entity
Dividend income	5	5	9	9
Dividend distributions	5	5	9	9
Trust V
Variable Interest Entity
Dividend income	4	4	8	5
Dividend distributions	4	$ 4	8	$ 5
Trust VI
Variable Interest Entity
Dividend income	0		0
Dividend distributions	$ 0		$ 0