Pension and Other Postretirement Benefits-Post Retirement Benefit Cost (Details) - Other Postretirement Benefit Plan, Defined Benefit [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Interest Cost	$ 1	$ 1
Amortization of reduction in liability resulting from plan amendment	(2)	(2)
Net periodic postretirement benefit cost	$ (1)	$ (1)