Postretirement Benefit Plans (Summary of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net periodic benefit cost:
Amortization of net actuarial loss	$ 1
Net periodic benefit cost	7	$ 1
Domestic defined benefit pension plans
Net periodic benefit cost:
Service cost	1	1
Interest cost	1	1
Expected return on plan assets	(2)	(2)
Amortization of net actuarial loss	1
Net periodic benefit cost	1
International defined benefit pension plans
Net periodic benefit cost:
Service cost	3	3
Interest cost	4	5
Expected return on plan assets	(4)	(9)
Amortization of net actuarial loss	3	2
Net periodic benefit cost	$ 6	$ 1