Compensation and Benefit Plans (Effect of Change in One Percent) (Details) - Postretirement Benefits Other Than Pensions $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Effect on ABO of one-percentage-point increase in assumed health care cost trend rate	$ 247
Effect on ABO of one-percentage-point decrease in assumed health care cost trend rate	(203)
Effect on annual aggregate service and interest costs of one-percentage-point increase in assumed health care cost trend rate	9
Effect on annual aggregate service and interest costs of one-percentage-point decrease in assumed health care cost trend rate	(8)
SCE
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Effect on ABO of one-percentage-point increase in assumed health care cost trend rate	246
Effect on ABO of one-percentage-point decrease in assumed health care cost trend rate	(202)
Effect on annual aggregate service and interest costs of one-percentage-point increase in assumed health care cost trend rate	9
Effect on annual aggregate service and interest costs of one-percentage-point decrease in assumed health care cost trend rate	$ (8)

Amount of decrease in accumulated postretirement benefit obligation from one-percentage-point decrease in assumed health care cost trend rate.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (m)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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Amount of decrease in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point decrease in assumed health care cost trend rate.

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Amount of increase in accumulated postretirement benefit obligation from one-percentage-point increase in assumed health care cost trend rate.

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