Retirement Benefits (Net Periodic Benefit Costs Schedule) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	$ 0	$ 0
Defined Benefit Plan, Interest Cost	3	1
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	2	0
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	1	1
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	1	1
Defined Benefit Plan, Interest Cost	7	5
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	10	10
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	26	16
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 24	$ 12