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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, 2018 | Dec. 31, 2017
--- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |
Investments measured at NAV | $ 6,813 | $ 8,980
Total investments | 14,378 | 16,176
Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Total investments | 2,970 | 2,586
Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Total investments | 4,261 | 4,238
Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Total investments | 334 | 372
Common/Collective trusts |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 5,620 | 7,986
Investments measured at NAV | 5,329 | 7,611
Common/Collective trusts | Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 291 | 375
Common/Collective trusts | Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Common/Collective trusts | Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Corporate Obligations |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 3,673 | 3,640
Investments measured at NAV | 0 | 0
Corporate Obligations | Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Corporate Obligations | Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 3,673 | 3,620
Corporate Obligations | Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 20
Corporate stocks |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 2,080 | 1,503
Investments measured at NAV | 0 | 0
Corporate stocks | Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 2,046 | 1,467
Corporate stocks | Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 33 | 34
Corporate stocks | Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 1 | 2
Private equity/partnerships |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 921 | 803
Investments measured at NAV | 921 | 803
Private equity/partnerships | Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Private equity/partnerships | Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Private equity/partnerships | Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Government Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 550 | 571
Investments measured at NAV | 0 | 0
Government Securities | Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 15 | 15
Government Securities | Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 535 | 556
Government Securities | 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 | 563 | 566
Investments measured at NAV | 563 | 566
Real Estate | Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Real Estate | Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Real Estate | Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Short-term investment funds |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 286 | 407
Investments measured at NAV | 0 | 0
Short-term investment funds | Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 286 | 391
Short-term investment funds | Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 16
Short-term investment funds | 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 | 319 | 326
Investments measured at NAV | 0 | 0
Company common stock | Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 319 | 326
Company common stock | Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0 | 0
Company common stock | 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 | 366 | 374
Investments measured at NAV | 0 | 0
Other Investments | Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 13 | 12
Other Investments | Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 20 | 12
Other Investments | Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | $ 333 | $ 350

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