Retirement Benefits (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
United States
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 0	$ 0
Interest cost	3	2	3
Expected return on plan assets	(3)	(3)	(3)
Prior service cost amortization	0	0	0
Recognized actuarial loss	2	2	1
Net periodic benefit cost	2	1	1
Int’l
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	2	1
Interest cost	50	50	53
Expected return on plan assets	(77)	(80)	(77)
Prior service cost amortization	1	0	0
Recognized actuarial loss	16	26	30
Net periodic benefit cost	$ (8)	$ (2)	$ 7