Employee Benefits - Components of net periodic benefit cost (Details) £ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 GBP (£)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 GBP (£)
U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlement expense	$ (170)
Pension Plan | U.S.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	0	$ 0		$ 0
Interest cost	73	57		85
Expected return on plan assets, net of administration expenses	(108)	(130)		(134)
Amortization of prior-service cost	0	0		1
Amortization of net actuarial loss	61	78		68
Net periodic benefit (income) cost	26	5		20
Settlement expense	170	0		0
Total net periodic benefit cost (income)	196	5		20
Pension Plan | U.K.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	1	1		0
Interest cost	83	65		88
Expected return on plan assets, net of administration expenses	(134)	(137)		(159)
Amortization of prior-service cost	2	2		2
Amortization of net actuarial loss	29	32		30
Net periodic benefit (income) cost	(19)	(37)		(39)
Settlement expense	0	5	£ 3	2	£ 2
Total net periodic benefit cost (income)	(19)	(32)		(37)
Pension Plan | Other
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	0	0		0
Interest cost	19	12		19
Expected return on plan assets, net of administration expenses	(33)	(32)		(34)
Amortization of prior-service cost	0	0		0
Amortization of net actuarial loss	13	15		12
Net periodic benefit (income) cost	(1)	(5)		(3)
Settlement expense	0	0		0
Total net periodic benefit cost (income)	$ (1)	$ (5)		$ (3)