Retirement Benefits (Summary of the U.S. and Non-U.S. Plan Investments Measured At Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 17,085	$ 14,378
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,930	2,970
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,796	4,261
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	683	334
NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,676	6,813
Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,451	5,620
Common/collective trusts | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	492	291
Common/collective trusts | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Common/collective trusts | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Common/collective trusts | NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,959	5,329
Corporate obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,063	3,673
Corporate obligations | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Corporate obligations | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,063	3,673
Corporate obligations | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Corporate stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,906	2,080
Corporate stocks | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,871	2,046
Corporate stocks | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	34	33
Corporate stocks | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	1
Private equity/partnerships
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,055	921
Private equity/partnerships | NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,055	921
Government securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	699	550
Government securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	20	15
Government securities | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	679	535
Government securities | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	660	563
Real estate | NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	660	563
Short-term investment funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	312	286
Short-term investment funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	309	286
Short-term investment funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	0
Short-term investment funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Company common stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	223	319
Company common stock | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	223	319
Company common stock | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Company common stock | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	716	366
Other investments | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15	13
Other investments | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	17	20
Other investments | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	682	$ 333
Other investments | NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 2