Pension Plan and Other Postretirement Benefits (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Employer contributions			$ 12
Pension
Defined Benefit Plan Disclosure [Line Items]
Special termination benefits cost			7
Settlement loss	$ 0	$ 0	1	$ 0
Lump sum payments from pension plan			6
Decrease to pension liability due to settlement			3
Net periodic benefit cost	1	2	1	5
Benefit obligation	17		17		$ 33
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	1	$ 1	1	$ 2
Benefit obligation	$ 14		$ 14		$ 13
Non-Qualified Supplemental Employee Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Treasury stock acquired (in shares)			2,035		3,632