Employee Benefit Plans - Postretirement (Details) - Other Postretirement Benefit Plan, Defined Benefit [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 0	$ 0
Prior service cost (benefit)	(4)	(5)
Actuarial loss	1	1
Net benefit cost	(3)	$ (4)
Defined Benefit Plan, Contributions by Employer	1
Defined Benefit Plan Estimated Total Employer Contributions in Current Fiscal Year	3
Defined Benefit Plans, Estimated Future Employer Contributions in Current Fiscal Year	$ 2