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Retirement Benefits (Schedule Of Allocation Of Plan Assets) (Details) - USD ($) $ in Millions | Dec. 31, 2016 | Dec. 31, 2015
--- | --- | ---
DB Pension Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | $ 2,101 | $ 2,013
DB Pension Plan [Member] | Cash and Short-Term Investments [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 110 | 215
DB Pension Plan [Member] | Cash and Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 110 | 215
DB Pension Plan [Member] | U.S. Government and Agencies Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 1 | 19
DB Pension Plan [Member] | U.S. Government and Agencies Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 1 | 19
DB Pension Plan [Member] | Corporate Debt [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 266 | 243
DB Pension Plan [Member] | Corporate Debt [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 266 | 243
DB Pension Plan [Member] | State and Municipal Bonds [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 9 | 8
DB Pension Plan [Member] | State and Municipal Bonds [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 9 | 8
DB Pension Plan [Member] | Foreign Corporate Debt [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 25 | 16
DB Pension Plan [Member] | Foreign Corporate Debt [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 25 | 16
DB Pension Plan [Member] | Mutual Funds [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 571 | 538
DB Pension Plan [Member] | Mutual Funds [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 571 | 538
DB Pension Plan [Member] | Plan Assets Excluding Pooled Funds [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 982 | 1,039
DB Pension Plan [Member] | Plan Assets Excluding Pooled Funds [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 681 | 753
DB Pension Plan [Member] | Plan Assets Excluding Pooled Funds [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 301 | 286
DB Pension Plan [Member] | Pooled Funds [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 1,119 | 974
OPEB [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 1,264 | 1,208
OPEB [Member] | Cash and Short-Term Investments [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 39 | 51
OPEB [Member] | Cash and Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 39 | 51
OPEB [Member] | U.S. Government and Agencies Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits |  | 3
OPEB [Member] | U.S. Government and Agencies Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits |  | 3
OPEB [Member] | Corporate Debt [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 38 | 34
OPEB [Member] | Corporate Debt [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 38 | 34
OPEB [Member] | State and Municipal Bonds [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 1 | 1
OPEB [Member] | State and Municipal Bonds [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 1 | 1
OPEB [Member] | Foreign Corporate Debt [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 4 | 2
OPEB [Member] | Foreign Corporate Debt [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 4 | 2
OPEB [Member] | Common Stocks [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 44 | 54
OPEB [Member] | Common Stocks [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 44 | 54
OPEB [Member] | Mutual Funds [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 563 | 456
OPEB [Member] | Mutual Funds [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 563 | 456
OPEB [Member] | Plan Assets Excluding Pooled Funds [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 689 | 601
OPEB [Member] | Plan Assets Excluding Pooled Funds [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 646 | 561
OPEB [Member] | Plan Assets Excluding Pooled Funds [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | 43 | 40
OPEB [Member] | Pooled Funds [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Defined Benefit Plan, Assets for Plan Benefits | $ 575 | $ 607

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