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