Fair Value Measurements (Level 3 Rollforward) (Details) - SCE - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Total realized/unrealized gains:
Reclassified derivative liabilities	$ 914
Level 3
Fair Value Disclosures Level 3 [Roll Forward]
Fair value of net assets (liabilities) at beginning of period		$ 101	$ (1,089)
Total realized/unrealized gains:
Included in regulatory assets and liabilities		40	133
Contract amendment		0	143
Normal purchase and normal sale designation		0	914
Fair value of net assets at end of period		141	101
Change during the period in unrealized gains and losses related to assets and liabilities held at the end of the period		$ 138	$ 100