Income Taxes (Interest and Penalties Related to Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Line Items]
Accrued interest and penalties	$ 115	$ 128
Net after-tax interest and penalties tax expense (benefit)	6	6	$ (9)
SCE
Income Tax Disclosure [Line Items]
Accrued interest and penalties	41	41
Net after-tax interest and penalties tax expense (benefit)	$ 4	$ 2	$ (14)