Revenue (Activities in the Allowance for Doubtful Accounts) (Details) - Southern California Edison $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at January 1,	$ 36
Charged to costs and expenses	7
Write-offs	(6)
Balance at March 31,	$ 37