Retirement Benefits - Benefit Obligations and Plan Assets in Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Other current liabilities	$ 15	$ 47
Pension obligations	1,571	1,109
Non-pension postretirement benefit obligations	0	0
Unfunded status (net benefit obligation less plan assets)	1,586	1,156
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Other current liabilities	26	26
Pension obligations	0	0
Non-pension postretirement benefit obligations	527	507
Unfunded status (net benefit obligation less plan assets)	$ 553	$ 533