Benefit Plans - Postemployment Benefit Costs (Details) - Postemployment Benefit Plans - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1	$ 1
Interest cost	1	1
Amortization of net gains	(1)	(1)
Net periodic benefit costs	$ 1	$ 1