Retirement Benefits - Net Benefit Costs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Defined Benefit Plan Disclosure
Settlement			$ 0	$ 26
Pension benefits | US
Defined Benefit Plan Disclosure
Service cost	$ 0	$ 0	0	0
Interest cost	2	3	3	5
Expected return on plan assets	(2)	(3)	(5)	(6)
Settlement	0	26	0	26
Amortization of unrecognized prior service credit	0	0	0	0
Amortization of unrecognized loss	0	1	1	2
Net periodic benefit cost	0	27	(1)	27
Pension benefits | Non-US
Defined Benefit Plan Disclosure
Service cost	5	4	10	9
Interest cost	3	3	5	6
Expected return on plan assets	(6)	(6)	(12)	(11)
Settlement	0	0	0	0
Amortization of unrecognized prior service credit	0	0	0	0
Amortization of unrecognized loss	2	3	5	5
Net periodic benefit cost	4	4	8	9
Other postretirement employee benefits
Defined Benefit Plan Disclosure
Service cost	0	0	0	0
Interest cost	0	1	1	2
Expected return on plan assets	0	0	0	0
Settlement	0	0	0	0
Amortization of unrecognized prior service credit	0	(1)	(1)	(2)
Amortization of unrecognized loss	0	0	0	0
Net periodic benefit cost	$ 0	$ 0	$ 0	$ 0