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Income Taxes (Components of Net Accumulated Deferred Income Tax Liability) (Details) - USD ($) $ in Millions | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Deferred tax assets: |  |  |  |
Property and software related | $ 358 | $ 549 |  |
Nuclear decommissioning trust assets in excess of nuclear ARO liability | 404 | 348 |  |
Loss and credit carryforwards | 1,346 | 1,418 |  |
Regulatory asset | 812 | 15 |  |
Pension and postretirement benefits other than pensions | 214 | 300 |  |
Other | 277 | 419 |  |
Sub-total | 3,411 | 3,049 |  |
Less valuation allowance | 28 | 24 |  |
Total | 3,383 | 3,025 |  |
Deferred tax liabilities: |  |  |  |
Property-related | 6,970 | 10,330 |  |
Capitalized software costs | 160 | 237 |  |
Regulatory liability | 158 | 134 |  |
Nuclear decommissioning trust assets | 404 | 348 |  |
Postretirement benefits other than pensions | 36 | 13 |  |
Other | 140 | 202 |  |
Total | 7,868 | 11,264 |  |
Accumulated deferred income tax liability, net | 4,485 | 8,239 |  |
Recorded valuation allowance | 28 |  |  |
Unrecognized tax benefits | 432 | 471 | $ 529 | $ 576
Regulatory asset | 809 |  |  |
Loss And Credit Carryforwards |  |  |  |
Deferred tax liabilities: |  |  |  |
Unrecognized tax benefits | 77 |  |  |
SCE |  |  |  |
Deferred tax assets: |  |  |  |
Property and software related | 357 | 548 |  |
Nuclear decommissioning trust assets in excess of nuclear ARO liability | 404 | 348 |  |
Loss and credit carryforwards | 150 | 0 |  |
Regulatory asset | 812 | 15 |  |
Pension and postretirement benefits other than pensions | 86 | 93 |  |
Other | 236 | 408 |  |
Sub-total | 2,045 | 1,412 |  |
Less valuation allowance | 0 | 0 |  |
Total | 2,045 | 1,412 |  |
Deferred tax liabilities: |  |  |  |
Property-related | 6,962 | 10,330 |  |
Capitalized software costs | 160 | 237 |  |
Regulatory liability | 158 | 134 |  |
Nuclear decommissioning trust assets | 404 | 348 |  |
Postretirement benefits other than pensions | 36 | 13 |  |
Other | 133 | 148 |  |
Total | 7,853 | 11,210 |  |
Accumulated deferred income tax liability, net | 5,808 | 9,798 |  |
Unrecognized tax benefits | 331 | $ 371 | $ 353 | $ 441
SCE | Loss And Credit Carryforwards |  |  |  |
Deferred tax liabilities: |  |  |  |
Unrecognized tax benefits | $ 75 |  |  |

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