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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 2	$ 4	$ 4
Interest cost	1	1	2	2
Expected return on plan assets	(2)	(1)	(3)	(3)
Amortization of prior service cost	0	0	0	0
Amortization of net loss	0	0	0	1
Settlement loss	0	4	0	4
Net periodic benefit cost	$ 1	$ 6	$ 3	$ 8