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Retirement Benefits (Narrative) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	Dec. 31, 2024	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer		$ 17	$ 27	$ 35	$ 51
Estimated future employer contributions in current fiscal year		45		45
United States
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, cost recognized		52	48	108	97
United Kingdom
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, cost recognized		$ 42	$ 39	$ 98	$ 91
United Kingdom \| Pension and Postretirement Benefit Plan, Defined Benefit \| Geographic Concentration Risk
Defined Benefit Plan Disclosure [Line Items]
Concentration risk percentage (as a percent)	78.00%
Equity Funds \| United States
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation, percentage (as a percent)		50.00%		50.00%
Actual asset allocation percentage of equity (as a percent)		51.00%		51.00%
Equity Funds \| United Kingdom
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation, percentage (as a percent)		12.00%		12.00%
Actual asset allocation percentage of equity (as a percent)		9.00%		9.00%
Fixed Income Funds \| United States
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation, percentage (as a percent)		50.00%		50.00%
Actual asset allocation percentage of equity (as a percent)		49.00%		49.00%
Fixed Income Funds \| United Kingdom
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation, percentage (as a percent)		88.00%		88.00%
Actual asset allocation percentage of equity (as a percent)		91.00%		91.00%