Summary of Significant Accounting Policies (New Accounting Guidance) (Details) - USD ($) $ in Millions			12 Months Ended
	Jan. 01, 2019	Jan. 01, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted cash			$ 8	$ 41
SCE
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net periodic benefit income – non-service components			$ 81	51	$ 35
ASU 2016-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting changes		$ 5
Cumulative effect of accounting changes, before tax		8
ASU 2018-14 | Operation and maintenance
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net periodic benefit income – non-service components				(37)	(30)
ASU 2018-14 | Other income and expenses
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net periodic benefit income – non-service components				37	30
ASU 2018-14 | SCE | Operation and maintenance
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net periodic benefit income – non-service components				(51)	(35)
ASU 2018-14 | SCE | Other income and expenses
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net periodic benefit income – non-service components				$ 51	$ 35
ASU 2018-02 | Forecast
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of stranded tax effects	$ 10
ASU 2018-02 | SCE | Forecast
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of stranded tax effects	5
Difference between revenue guidance in effect before and after topic 606 | ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting changes		5
Cumulative effect of accounting changes, before tax		$ 7
Subsequent event | ASU 2016-02 | Forecast
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use assets	1,000
Right-of-use lease liabilities	1,000
Subsequent event | ASU 2016-02 | SCE | Forecast
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use assets	1,000
Right-of-use lease liabilities	$ 1,000