Pension Plan And Other Postretirement Benefits (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Mar. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Employer contributions			$ 8
Company's expected additional annual contribution	$ 6		$ 6
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)		$ (1)
Settlement loss		(8)		(8)
Net periodic benefit cost (gain)	$ 2	12	$ 5	16
Curtailment gain (loss)		$ (1)		$ (1)
Benefit obligation	33		33		$ 36
Discount rate		4.20%		4.20%		4.60%
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Non-cash curtailment gain (loss)		$ 6		$ 6
Net periodic benefit cost (gain)		6	1	(5)
Curtailment gain (loss)		$ 6		$ 6
Benefit obligation	$ 14		$ 14		$ 13
Discount rate		4.20%		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			11,686		31,269