Pension Plan And Other Postretirement Benefits (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Employer contributions			$ 11
Company's expected additional annual contribution	$ 3		$ 3
Common Stock in Treasury, Shares	31,269		31,269		31,269
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Non-cash curtailment gain (loss)				$ (1)
Settlement loss		$ (2)		(10)
Net periodic benefit cost (gain)	$ 3	4	$ 8	20
Curtailment gain (loss)				(1)
Benefit obligation	32		32		$ 36
Discount rate						4.20%	4.60%
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Non-cash curtailment gain (loss)				6
Net periodic benefit cost (gain)	1	$ 1	2	(4)
Curtailment gain (loss)				$ 6
Benefit obligation	$ 14		$ 14		$ 13
Discount rate						4.20%	4.60%
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Common stock purchased under the terms of the Non-Qualified Plan presented as treasury stock			10,652		31,269