Pension and Other Postretirement Benefits-Projected Benefit Obligation (Details) - Other Postretirement Benefit Plan, Defined Benefit [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Accumulated benefit obligation at beginning of year	$ 100	$ 173
Interest cost	4	5
Actuarial gains	(6)	(21)
Reduction in liability resulting from plan amendment	0	(46)
Benefits paid, net	(7)	(11)
Accumulated benefit obligation at end of year	$ 91	$ 100