Pension Plan And Other Postretirement Benefits (Pension And Other Postretirement Benefit Costs) (Details) - Pension Benefits [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 4
Interest cost	1	2
Expected return on plan assets	(1)	(2)
Amortization of prior service cost
Amortization of net loss	1
Net periodic benefit cost	$ 3	$ 4