Pension Plan and Other Postretirement Benefits (Pension and Other Postretirement Benefit Costs) (Details) - Pension - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 2	$ 0	$ 6
Interest cost	1	1	3	3
Expected return on plan assets	0	(2)	(3)	(5)
Amortization of net loss	0	1	0	1
Settlement loss	0	0	1	0
Net periodic benefit cost	$ 1	$ 2	$ 1	$ 5