Retirement Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Allocated Service Cost	$ 41	$ 54	$ 61
Defined Contribution Plan, Cost	10	9	8
Other Postretirement Benefits Cost (Reversal of Cost)	$ 2	$ 3	$ 3