Pension Plan and Other Postretirement Benefits (Narrative) (Details) - USD ($)	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Employer contributions				$ 12,000,000
Treasury stock acquired (in shares)			5,260,687
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost (gain)	$ 1,000,000	$ 1,000,000		2,000,000	$ 1,000,000
Benefit obligation	14,000,000			14,000,000		$ 13,000,000
Pension
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost (gain)	2,000,000	3,000,000		5,000,000	11,000,000
Expected future employer contributions, remainder of fiscal year	0			0
Benefit obligation	22,000,000			22,000,000		$ 30,000,000
Settlement loss	$ 0	$ 1,000,000		$ 0	5,000,000
Payments for pension plan					$ 19,000,000
Non-Qualified Supplemental Employee Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Treasury stock acquired (in shares)				3,632		5,115