Variable Interest Entities (Summary of Trusts' Income Statement) (Details) - Variable Interest Entity, Not Primary Beneficiary - Southern California Edison - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Trust I
Variable Interest Entity
Dividend income	$ 7	$ 7	$ 20	$ 20
Dividend distributions	7	7	20	20
Trust II
Variable Interest Entity
Dividend income	5	5	15	15
Dividend distributions	5	5	15	15
Trust III
Variable Interest Entity
Dividend income	4	4	12	12
Dividend distributions	4	4	12	12
Trust IV
Variable Interest Entity
Dividend income	4	2	13	2
Dividend distributions	4	$ 2	13	$ 2
Trust V
Variable Interest Entity
Dividend income	4		9
Dividend distributions	$ 4		$ 9