Retirement Benefits - Net Benefit Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plan Disclosure
Settlement loss			$ 0	$ 26
Pension benefits | US
Defined Benefit Plan Disclosure
Service cost	$ 0	$ 0	0	0
Interest cost	1	2	4	7
Expected return on plan assets	(2)	(3)	(7)	(9)
Settlement loss			0	26
Amortization of unrecognized prior service credit	(1)	(1)	(1)	(1)
Amortization of unrecognized loss	1	2	2	4
Net periodic benefit cost	(1)	0	(2)	27
Pension benefits | Non-US
Defined Benefit Plan Disclosure
Service cost	5	5	15	14
Interest cost	2	3	7	9
Expected return on plan assets	(6)	(6)	(18)	(17)
Settlement loss			0	0
Amortization of unrecognized prior service credit	0	0	0	0
Amortization of unrecognized loss	3	2	8	7
Net periodic benefit cost	4	4	12	13
Other postretirement employee benefits
Defined Benefit Plan Disclosure
Service cost	0	0	0	0
Interest cost	0	0	1	2
Expected return on plan assets	0	0	0	0
Settlement loss			0	0
Amortization of unrecognized prior service credit	(1)	(1)	(2)	(3)
Amortization of unrecognized loss	1	1	1	1
Net periodic benefit cost	$ 0	$ 0	$ 0	$ 0