Fair Value Measurements (Level 3 Rollforward) (Details) - Southern California Edison - Level 3 - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Fair Value Disclosures Level 3 [Roll Forward]
Fair value of net liabilities at beginning of period	$ (1,089)	$ (1,148)
Total realized/unrealized losses:
Included in regulatory assets and liabilities	(77)	(65)
Fair value of net liabilities at end of period	(1,166)	(1,213)
Change during the period in unrealized losses related to assets and liabilities held at the end of the period	$ (102)	$ (84)