Pension Plan and Other Postretirement Benefits (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Employer contributions				$ 9
Treasury stock acquired (in shares)			5,260,687
Pension
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost (gain)	$ 1	$ 6		3	$ 8
Additional contributions for remainder of year	3			3
Benefit obligation	24			24		$ 30
Settlement loss	0	4		0	4
Payments for pension plan					16
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost (gain)	1	$ 1		1	$ 1
Benefit obligation	$ 14			$ 14		$ 13
Non-Qualified Supplemental Employee Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Treasury stock acquired (in shares)				3,632		5,115