Benefit Plans - Postemployment Benefit Costs (Details) - Postemployment Benefit Plans - 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 [Line Items]
Service cost	$ 2	$ 2	$ 3	$ 3
Interest cost	1	1	2	2
Amortization of net gains	(1)	0	(2)	(1)
Net periodic benefit costs	$ 2	$ 3	$ 3	$ 4