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Compensation and Benefit Plans (Textual) (Details) - USD ($) shares in Millions, $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Assumed average equity risk premium (percent) | 5.00% |  |
Forecasted return on private equity and opportunistic investments (percent) | 2.00% |  |
Performance incentive plan award (shares) | 66 |  |
Share-based compensation, shares available for grant | 30 |  |
Stock options |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Stock options, expiration period, years | 10 years |  |
Stock options, vesting period, years | 4 years |  |
Volatility period | 68 months | 71 months | 71 months
Pension Plans |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Expected contributions | $ 66 |  |
Permissible range of asset class weights (percent) | 3.00% |  |
Publicly traded equity investments located in the US (percent) | 67.00% | 69.00% |
Pension Plans | US Equities |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Target plan asset allocations (percent) | 29.00% |  |
Pension Plans | Non-US Equities |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Target plan asset allocations (percent) | 17.00% |  |
Pension Plans | Fixed Income |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Target plan asset allocations (percent) | 35.00% |  |
Pension Plans | Opportunistic Alternative Investments |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Target plan asset allocations (percent) | 15.00% |  |
Pension Plans | Other Investments |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Target plan asset allocations (percent) | 4.00% |  |
Postretirement Benefits Other Than Pensions |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Expected contributions | $ 12 |  |
Eligibility age | 55 years |  |
Service period for eligibility (at least) (years) | 10 years |  |
Publicly traded equity investments located in the US (percent) | 61.00% | 63.00% |
Postretirement Benefits Other Than Pensions | US Equities |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Target plan asset allocations (percent) | 58.00% |  |
Postretirement Benefits Other Than Pensions | Fixed Income |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Target plan asset allocations (percent) | 29.00% |  |
Postretirement Benefits Other Than Pensions | Opportunistic Alternative Investments |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Target plan asset allocations (percent) | 13.00% |  |
Voluntary Employee Beneficiary Association (VEBA) | Fixed Income |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Target plan asset allocations (percent) | 85.00% |  |
Voluntary Employee Beneficiary Association (VEBA) | Opportunistic Alternative Investments |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Target plan asset allocations (percent) | 5.00% |  |
Voluntary Employee Beneficiary Association (VEBA) | Global Equities |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Target plan asset allocations (percent) | 10.00% |  |
SCE | Pension Plans |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Expected contributions | $ 50 |  |

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- Definition The actual asset allocation of fair value of publicly traded equity investments. + References No definition available. + Details
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- Definition Amount of contributions expected to be received by defined benefit plan from employer in next fiscal year following latest fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5)(i) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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