Employee Benefit Plans, Benefit Payments (Details) $ in Millions	Dec. 31, 2017 USD ($)
Pension Plans [Member]
Estimated Future Benefit Payments
2018	$ 162
2019	219
2020	184
2021	180
2022	185
2023-2027	1,074
Employee Benefit Plans (Textual)
Future employer contributions to pension and other postretirement plans	131
Future employer discretionary contributions to pension plan	100
Other Postretirement Benefit Plans [Member]
Estimated Future Benefit Payments
2018	19
2019	19
2020	19
2021	19
2022	19
2023-2027	93
Employee Benefit Plans (Textual)
Future employer contributions to pension and other postretirement plans	$ 19