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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, 2017 | Dec. 31, 2016
--- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |
Investments measured at NAV | $ 8,980 | $ 7,939
Total investments | 16,176 | 14,332
Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Total investments | 2,586 | 2,618
Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Total investments | 4,238 | 3,452
Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Total investments | 372 | 323
Common/Collective trusts |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 7,986 | 6,821
Investments measured at NAV | 7,611 | 6,805
Common/Collective trusts | Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 375 | 16
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 | 3,640 | 3,033
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 | 3,620 | 3,024
Corporate Obligations | Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 20 | 9
Corporate stocks |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 1,503 | 2,014
Investments measured at NAV | 0 | 0
Corporate stocks | Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 1,467 | 2,009
Corporate stocks | Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 34 | 3
Corporate stocks | Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 2 | 2
Private equity/partnerships |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 803 | 722
Investments measured at NAV | 803 | 722
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 | 571 | 391
Investments measured at NAV | 0 | 0
Government Securities | Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 15 | 11
Government Securities | Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 556 | 380
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 | 566 | 412
Investments measured at NAV | 566 | 412
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 | 407 | 319
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 | 391 | 297
Short-term investment funds | Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 16 | 22
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 | 326 | 270
Investments measured at NAV | 0 | 0
Company common stock | Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 326 | 270
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 | 374 | 350
Investments measured at NAV | 0 | 0
Other Investments | Identical Assets (Level 1) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 12 | 15
Other Investments | Observable Inputs (Level 2) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 12 | 23
Other Investments | Unobservable Inputs (Level 3) |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | $ 350 | $ 312

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