Pensions and Other Postretirement Benefits-Projected Benefit Obligation (Details) - Postretirement Plans Other Than Pensions [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Accumulated benefit obligation at beginning of year	$ 45	$ 42
Interest cost	1	2	$ 2
Actuarial losses	2	5
Benefits paid, net	(3)	(4)
Accumulated benefit obligation at end of year	$ 45	$ 45	$ 42