Retirement Benefits - Net Periodic Benefit Cost (Details) - Pension Plan [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 14	$ 19
Interest cost	49	29
Expected return on plan assets	(76)	(83)
Amortization of net loss	3	4
Amortization of prior service credit	0	0
Net periodic benefit (income)/cost	(10)	(31)
United Kingdom [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	3
Interest cost	29	19
Expected return on plan assets	(39)	(39)
Amortization of net loss	12	8
Amortization of prior service credit	(3)	(3)
Net periodic benefit (income)/cost	0	(12)
Other Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	3	6
Interest cost	7	4
Expected return on plan assets	(9)	(10)
Amortization of net loss	0	1
Amortization of prior service credit	0	0
Net periodic benefit (income)/cost	$ 1	$ 1