Employee Benefit Plans (Details) - Other Postretirement Benefit Plans, Defined Benefit [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 2	$ 3
Expected return on plan assets	(1)	(1)
Amortization of prior service credit	(1)	(1)
Net periodic cost	0	$ 1
Expected contribution to postretirement benefit plan in current year	9
Total contribution to the plan during the period	$ 2