Benefit Plans (Components of Pension and Other Employee Benefits Costs) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total pension and other employee benefit costs	$ 23	$ 20	$ 68	$ 61
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total pension and other employee benefit costs	(5)	(6)	(13)	(16)
Postemployment Benefit Plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total pension and other employee benefit costs	26	25	75	72
Postretirement Benefit Costs [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total pension and other employee benefit costs	$ 2	$ 1	$ 6	$ 5