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Retirement Benefits (Narrative) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Dec. 31, 2022	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer		$ 26	$ 28	$ 73	$ 141
Estimated future employer contributions in current fiscal year		35		35
United States
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, cost recognized		45	39	133	122
United Kingdom
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, cost recognized		$ 39	$ 31	$ 120	$ 108
United Kingdom \| Non-U.S. Plans \| Geographic Concentration Risk
Defined Benefit Plan Disclosure [Line Items]
Concentration risk percentage	79.00%
Equity Funds \| United States
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation, percentage		50.00%		50.00%
Actual asset allocation percentage of equity		48.00%		48.00%
Equity Funds \| United Kingdom
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation, percentage		14.00%		14.00%
Actual asset allocation percentage of equity		14.00%		14.00%
Fixed Income Funds \| United States
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation, percentage		50.00%		50.00%
Actual asset allocation percentage of equity		52.00%		52.00%
Fixed Income Funds \| United Kingdom
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation, percentage		86.00%		86.00%
Actual asset allocation percentage of equity		86.00%		86.00%