Employee Retirement Plans (Domestic Defined Benefit Plan Assets) (Details) - Pension Benefits [Member] - United States [Member] - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 3,605	$ 3,153
Quoted Market Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	231	274
Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,183	2,670
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	191	209
Defined Benefit Plan, Equity Securities, US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	781	494
Defined Benefit Plan, Equity Securities, US [Member] | Quoted Market Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	2
Defined Benefit Plan, Equity Securities, US [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	780	492
Defined Benefit Plan, Equity Securities, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	441	387
Defined Benefit Plan, Equity Securities, Non-US [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	441	387
US Treasury Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	147
US Treasury Securities [Member] | Quoted Market Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	147
Debt Security, Corporate, US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,951	2,017
Debt Security, Corporate, US [Member] | Quoted Market Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		226
Debt Security, Corporate, US [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,951	1,791
Preferred Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11
Preferred Stock [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11
Private Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	51	64
Private Equity Funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	51	64
Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	140	145
Real Estate [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	140	145
Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	83	46
Cash Equivalents [Member] | Quoted Market Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 83	$ 46