Retirement Benefits - Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Pension Plan [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 19	$ 20	$ 38	$ 40
Interest cost	30	24	59	47
Expected return on plan assets	(82)	(77)	(165)	(154)
Settlement	0	0	0	1
Amortization of net loss	3	11	7	22
Amortization of prior service credit	0	0	0	0
Net periodic benefit (income)/cost	(30)	(22)	(61)	(44)
Pension Plan [Member] | United Kingdom [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	4	5	7	9
Interest cost	17	14	36	28
Expected return on plan assets	(37)	(43)	(76)	(86)
Settlement	0	1	0	1
Amortization of net loss	7	7	15	14
Amortization of prior service credit	(3)	(5)	(6)	(9)
Net periodic benefit (income)/cost	(12)	(21)	(24)	(43)
Pension Plan [Member] | Other Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	6	11	12
Interest cost	4	3	8	6
Expected return on plan assets	(9)	(10)	(19)	(19)
Settlement	0	0	0	0
Amortization of net loss	1	2	2	3
Amortization of prior service credit	0	0	0	0
Net periodic benefit (income)/cost	1	1	2	2
PRW [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	0	0
Interest cost	0	1	1	1
Expected return on plan assets	0	0	0	0
Settlement	0	0	0	0
Amortization of net loss	1	1	1	1
Amortization of prior service credit	(1)	(1)	(2)	(2)
Net periodic benefit (income)/cost	$ 0	$ 1	$ 0	$ 0