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Retirement Benefits (Narrative) (Details) - USD ($) $ in Millions |  | 3 Months Ended | 6 Months Ended
--- | --- | --- | ---
Dec. 31, 2021 | Jun. 30, 2022 | Jun. 30, 2021 | Jun. 30, 2022 | Jun. 30, 2021
Pension Benefits |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Contributions by employer |  | $ 45 | $ 28 | $ 113 | $ 57
Estimated future employer contributions in current fiscal year |  | 63 |  | 63 |
United States |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined contribution plan, cost recognized |  | 40 | 39 | 83 | 78
United Kingdom |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Defined contribution plan, cost recognized |  | $ 33 | $ 34 | $ 77 | $ 73
United Kingdom | Non-U.S. Plans | Geographic Concentration Risk |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Concentration risk percentage | 81.00% |  |  |  |
Equity Funds | United States |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Target asset allocation, percentage |  | 60.00% |  | 60.00% |
Actual asset allocation percentage of equity |  | 62.00% |  | 62.00% |
Equity Funds | United Kingdom |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Target asset allocation, percentage |  | 16.00% |  | 16.00% |
Actual asset allocation percentage of equity |  | 19.00% |  | 19.00% |
Fixed Income Funds | United States |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Target asset allocation, percentage |  | 40.00% |  | 40.00% |
Actual asset allocation percentage of equity |  | 38.00% |  | 38.00% |
Fixed Income Funds | United Kingdom |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Target asset allocation, percentage |  | 84.00% |  | 84.00% |
Actual asset allocation percentage of equity |  | 81.00% |  | 81.00% |

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