Pension Plan and Other Postretirement Benefits (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Employer contributions			$ 9
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	$ 1	$ 1	1	$ 1
Benefit obligation	14		14		$ 13
Pension
Defined Benefit Plan Disclosure [Line Items]
Settlement loss	1	0	1	0
Lump sum payments from pension plan			4
Decrease to pension liability due to settlement	3
Net periodic benefit cost	0	$ 1	0	$ 3
Expected future employer contributions, remainder of fiscal year	3		3
Benefit obligation	$ 21		$ 21		$ 33
Non-Qualified Supplemental Employee Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Treasury stock acquired (in shares)			2,035		3,632