Employee Benefit Plans (Schedule Of Fair Value Of Plan Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 2,337	$ 2,018
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	251	187
Equity Securities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	251	187
Mutual Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	666	575
Mutual Fund [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	666	575
Common collective trust funds - International equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	316	281
Common collective trust funds - U.S. equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	418	391
Debt instruments - Corporate bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	328	249
Debt instruments - Corporate bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	328	249
Debt instruments - U.S. Treasury instruments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	345	322
Debt instruments - U.S. Treasury instruments [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	345	322
Debt instruments - U.S. government agency, state and local government bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4	4
Debt instruments - U.S. government agency, state and local government bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4	4
Other Debt Instruments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9	9
Other Debt Instruments [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9	9
Fair Value, Recurring [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,603	1,346
Fair Value, Recurring [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,262	1,084
Fair Value, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 341	$ 262