Employee Benefits - Components of net periodic benefit cost (Details) £ in Millions, $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 GBP (£)
U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlement expense		$ (170)
Pension Plan | U.K.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		0	$ 1	$ 1
Interest cost		147	83	65
Expected return on plan assets, net of administration expenses		(190)	(134)	(137)
Amortization of prior-service cost		2	2	2
Amortization of net actuarial loss		75	29	32
Net periodic benefit (income) cost		34	(19)	(37)
Settlement expense		0	0	5	£ 3
Total net periodic benefit cost (income)		34	(19)	(32)
Pension Plan | Other
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		0	0	0
Interest cost		41	19	12
Expected return on plan assets, net of administration expenses		(48)	(33)	(32)
Amortization of prior-service cost		0	0	0
Amortization of net actuarial loss		13	13	15
Net periodic benefit (income) cost		6	(1)	(5)
Settlement expense	$ 27	27	0	0
Total net periodic benefit cost (income)		33	(1)	(5)
Pension Plan | U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		0	0	0
Interest cost		103	73	57
Expected return on plan assets, net of administration expenses		(119)	(108)	(130)
Amortization of prior-service cost		0	0	0
Amortization of net actuarial loss		34	61	78
Net periodic benefit (income) cost		18	26	5
Settlement expense		0	170	0
Total net periodic benefit cost (income)		$ 18	$ 196	$ 5