Pension Plan and Other Postretirement Benefits (Pension and Other Postretirement Benefit Costs) (Details) - Pension - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 2	$ 0	$ 4
Interest cost	1	1	2	2
Expected return on plan assets	(2)	(2)	(3)	(3)
Amortization of net loss	0	0	0	0
Settlement loss	1	0	1	0
Net periodic benefit cost	$ 0	$ 1	$ 0	$ 3