Postretirement Benefit Plans (Summary of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net periodic benefit cost:
Amortization of net actuarial loss	$ 1	$ 1	$ 2	$ 2
Net periodic benefit cost	12	1	13	5
Domestic defined benefit pension plans
Net periodic benefit cost:
Service cost	1		2	2
Interest cost	1	1	3	3
Expected return on plan assets	(2)	(2)	(6)	(5)
Amortization of net actuarial loss	0	1	1	2
Net periodic benefit cost	0		0	2
International defined benefit pension plans
Net periodic benefit cost:
Service cost	2	3	7	8
Interest cost	4	5	14	15
Expected return on plan assets	(4)	(9)	(22)	(28)
Amortization of net actuarial loss	2	2	6	7
Settlement/Curtailment	8	0	8	1
Net periodic benefit cost	$ 12	$ 1	$ 13	$ 3