Retirement Plans (Schedule Of Assets Measured At Fair Value On A Recurring Basis) (Details) - Pension [Member] - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 4,528	$ 3,887	$ 4,224
Temporary Cash Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		7	21
Registered Investment Companies [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	9	1
Federal Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		202	191
Bonds and Debentures [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		575	538
Corporate Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1,939	1,367
Total Plan Assets At Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2,732	2,118
Other Assets (Liabilities) - Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	12	(19)
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		6	21
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]	9	1
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		1,932	1,355
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		1,947	1,377
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		202	191
Significant Other Observable Inputs (Level 2) [Member] | Bonds and Debentures [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		575	538
Significant Other Observable Inputs (Level 2) [Member] | Corporate Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		7	12
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		785	741
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]	285	378
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		531	443
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		261	222
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		707	745
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		$ 1,784	$ 1,788

[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.