Compensation and Benefit Plans (Other Postretirement Plan Assets - Fair Value Levels) (Details) - Postretirement Benefits Other Than Pensions - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net plan assets available for benefits	$ 2,330	$ 2,102	$ 2,036
Corporate stocks | Russell Indexes
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Performance percentage benchmark, percentage	64.00%	47.00%
Corporate stocks | MSCI All Country World Index
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Performance percentage benchmark, percentage	36.00%	53.00%
Common/collective funds | MSCI-EAFE
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual plan asset allocations, percentage	75.00%	39.00%
Common/collective funds | Non-index U.S. equity fund
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual plan asset allocations, percentage	17.00%	18.00%
Partnerships | Private equity and venture capital funds including branded consumer products, clean and information technology and healthcare
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual plan asset allocations, percentage	56.00%	59.00%
Partnerships | Broad range of financial assets in all global markets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual plan asset allocations, percentage	33.00%	31.00%
Partnerships | Asset backed securities including distressed mortgages
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual plan asset allocations, percentage	9.00%	9.00%
Other | Municipal securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	$ 60	$ 76
Collateralized mortgage obligations and other asset backed securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Receivables and payables, net	36	47
SCE
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	2,349	2,133
Fair value NAV	651	542
Receivables and payables, net	(19)	(31)
Net plan assets available for benefits	2,330	2,102	$ 2,036
SCE | Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	736	552
SCE | Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	962	1,039
SCE | Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
SCE | U.S. government and agency securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	431	281
Fair value NAV	0	0
SCE | U.S. government and agency securities | Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	398	222
SCE | U.S. government and agency securities | Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	33	59
SCE | U.S. government and agency securities | Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
SCE | Corporate stocks
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	254	230
Fair value NAV	0	0
SCE | Corporate stocks | Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	254	230
SCE | Corporate stocks | Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
SCE | Corporate stocks | Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
SCE | Corporate notes and bonds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	845	877
Fair value NAV	0	0
SCE | Corporate notes and bonds | Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
SCE | Corporate notes and bonds | Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	845	877
SCE | Corporate notes and bonds | Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
SCE | Common/collective funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	569	462
Fair value NAV	569	462
SCE | Common/collective funds | Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
SCE | Common/collective funds | Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
SCE | Common/collective funds | Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
SCE | Partnerships
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	82	79
Fair value NAV	82	79
SCE | Partnerships | Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
SCE | Partnerships | Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
SCE | Partnerships | Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
SCE | Registered investment companies
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	37	49
Fair value NAV	0	1
SCE | Registered investment companies | Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	37	48
SCE | Registered investment companies | Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
SCE | Registered investment companies | Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
SCE | Interest bearing cash
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	42	48
Fair value NAV	0	0
SCE | Interest bearing cash | Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	42	48
SCE | Interest bearing cash | Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
SCE | Interest bearing cash | Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	0	0
SCE | Other
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	89	107
Fair value NAV	0	0
SCE | Other | Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	5	4
SCE | Other | Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	84	103
SCE | Other | Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	$ 0	$ 0