Employee Benefits - Reconciliation of the changes in the benefit obligations and fair value of assets and a statement of the funded status (Details) - Pension Plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
U.K.
Change in projected benefit obligation
Balance at the beginning of the Period	$ 2,946	$ 4,919
Service cost	0	1	$ 1
Interest cost	147	83	65
Plan amendment	5	0
Settlements	0	0
Actuarial (gain) loss	143	(1,418)
Benefit payments	(173)	(195)
Foreign currency impact	165	(444)
Balance at the end of the period	3,233	2,946	4,919
Accumulated benefit obligation at end of year	3,233	2,946
Change in fair value of plan assets
Balance at the beginning of the period	3,537	6,246
Actual return on plan assets	211	(1,961)
Employer contributions	4	7
Settlements	0	0
Benefit payments	(173)	(195)
Foreign currency impact	196	(559)
Balance at the end of the period	3,775	3,537	6,246
Market related value at end of year	3,775	3,537
Funded status	542	591
Unrecognized prior-service cost	39	35
Unrecognized loss	1,870	1,726
Net amount recognized	2,451	2,352
Other
Change in projected benefit obligation
Balance at the beginning of the Period	1,094	1,531
Service cost	0	0	0
Interest cost	41	19	12
Plan amendment	0	0
Settlements	(63)	0
Actuarial (gain) loss	63	(322)
Benefit payments	(44)	(45)
Foreign currency impact	38	(89)
Balance at the end of the period	1,129	1,094	1,531
Accumulated benefit obligation at end of year	1,117	1,079
Change in fair value of plan assets
Balance at the beginning of the period	1,032	1,430
Actual return on plan assets	93	(284)
Employer contributions	14	15
Settlements	(63)	0
Benefit payments	(44)	(45)
Foreign currency impact	37	(83)
Balance at the end of the period	1,069	1,032	1,430
Market related value at end of year	1,069	1,032
Funded status	(60)	(62)
Unrecognized prior-service cost	(5)	(6)
Unrecognized loss	436	443
Net amount recognized	371	375
U.S.
Change in projected benefit obligation
Balance at the beginning of the Period	2,180	3,164
Service cost	0	0	0
Interest cost	103	73	57
Plan amendment	0	0
Settlements	3	(283)
Actuarial (gain) loss	51	(607)
Benefit payments	(138)	(167)
Foreign currency impact	0	0
Balance at the end of the period	2,199	2,180	3,164
Accumulated benefit obligation at end of year	2,199	2,180
Change in fair value of plan assets
Balance at the beginning of the period	1,481	2,378
Actual return on plan assets	121	(484)
Employer contributions	32	37
Settlements	3	(283)
Benefit payments	(138)	(167)
Foreign currency impact	0	0
Balance at the end of the period	1,499	1,481	$ 2,378
Market related value at end of year	1,788	1,794
Funded status	(700)	(699)
Unrecognized prior-service cost	0	0
Unrecognized loss	1,319	1,305
Net amount recognized	$ 619	$ 606