Leases (Details) $ in Millions	Dec. 31, 2017 USD ($)
Leases [Abstract]
Operating Leases, Future Minimum Payments Due, Next Twelve Months	$ 217
Operating Leases, Future Minimum Payments, Due in Two Years	156
Operating Leases, Future Minimum Payments, Due in Three Years	115
Operating Leases, Future Minimum Payments, Due in Four Years	88
Operating Leases, Future Minimum Payments, Due in Five Years	68
Thereafter	178
Total minimum lease payments	$ 822