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Retirement Plans (Schedule Of Assets Measured At Fair Value On A Recurring Basis) (Details) - Pension [Member] - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  | $ 5,016 | $ 4,528 | $ 3,887
Temporary Cash Investments [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  | 9 | 7 |
Registered Investment Companies [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets | [1] | 252 | 9 |
Federal Government Securities [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  | 150 | 202 |
Bonds and Debentures [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  | 831 | 575 |
Corporate Stock [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  | 2,217 | 1,939 |
Total Plan Assets At Fair Value [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  | 3,459 | 2,732 |
Other Assets (Liabilities) - Pension Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets | [2] | 1 | 12 |
Quoted Prices in Active Markets for Identical Inputs (Level 1) [Member] | Temporary Cash Investments [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  | 9 | 6 |
Quoted Prices in Active Markets for Identical Inputs (Level 1) [Member] | Registered Investment Companies [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets | [1] | 252 | 9 |
Quoted Prices in Active Markets for Identical Inputs (Level 1) [Member] | Federal Government Securities [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  |  |  |
Quoted Prices in Active Markets for Identical Inputs (Level 1) [Member] | Bonds and Debentures [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  |  |  |
Quoted Prices in Active Markets for Identical Inputs (Level 1) [Member] | Corporate Stock [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  | 2,209 | 1,932 |
Quoted Prices in Active Markets for Identical Inputs (Level 1) [Member] | Total Plan Assets At Fair Value [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  | 2,470 | 1,947 |
Significant Other Observable Inputs (Level 2) [Member] | Temporary Cash Investments [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  |  | 1 |
Significant Other Observable Inputs (Level 2) [Member] | Registered Investment Companies [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets | [1] |  |  |
Significant Other Observable Inputs (Level 2) [Member] | Federal Government Securities [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  | 150 | 202 |
Significant Other Observable Inputs (Level 2) [Member] | Bonds and Debentures [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  | 831 | 575 |
Significant Other Observable Inputs (Level 2) [Member] | Corporate Stock [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  | 8 | 7 |
Significant Other Observable Inputs (Level 2) [Member] | Total Plan Assets At Fair Value [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  | 989 | 785 |
Significant Unobservable Inputs (Level 3) [Member] | Temporary Cash Investments [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  |  |  |
Significant Unobservable Inputs (Level 3) [Member] | Registered Investment Companies [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets | [1] |  |  |
Significant Unobservable Inputs (Level 3) [Member] | Federal Government Securities [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  |  |  |
Significant Unobservable Inputs (Level 3) [Member] | Bonds and Debentures [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  |  |  |
Significant Unobservable Inputs (Level 3) [Member] | Corporate Stock [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  |  |  |
Significant Unobservable Inputs (Level 3) [Member] | Total Plan Assets At Fair Value [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  |  |  |
Fair Value Measured at Net Asset Value Per Share [Member] | Registered Investment Companies - NAV [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets | [3] | 312 | 285 |
Fair Value Measured at Net Asset Value Per Share [Member] | Venture Capital And Buyout Partnerships [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  | 585 | 531 |
Fair Value Measured at Net Asset Value Per Share [Member] | Real Estate Partnerships [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  | 161 | 261 |
Fair Value Measured at Net Asset Value Per Share [Member] | Collective Trust And Other Funds [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  | 498 | 707 |
Fair Value Measured at Net Asset Value Per Share [Member] | Total Plan Assets at NAV [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Fair value of plan assets |  | $ 1,556 | $ 1,784 |
[1] | Registered investment companies measured at fair value are stock investments.
[2] | Other assets include accrued receivables, net payables, and pending broker settlements
[3] | Registered investment companies measured at NAV include bond investments.

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