Employee Benefits - Amounts recognized in the Consolidated Statements of Financial Position (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prepaid benefit cost	$ 618	$ 652
Pension Plan | U.K.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prepaid benefit cost	570	612
Accrued benefit liability - current	(1)	(1)
Accrued benefit liability - non-current	(27)	(20)
Accumulated other comprehensive loss	1,909	1,761
Net amount recognized	2,451	2,352
Pension Plan | Other
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prepaid benefit cost	1	0
Accrued benefit liability - current	(4)	(5)
Accrued benefit liability - non-current	(57)	(57)
Accumulated other comprehensive loss	431	437
Net amount recognized	371	375
Pension Plan | U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prepaid benefit cost	0	0
Accrued benefit liability - current	(42)	(42)
Accrued benefit liability - non-current	(658)	(657)
Accumulated other comprehensive loss	1,319	1,305
Net amount recognized	$ 619	$ 606