Leased Vehicles Minimum rental payments (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014
Operating Leases, Future Minimum Payments Receivable [Abstract]
Operating Leases, Future Minimum Payments Receivable, Current	$ 538
Operating Leases, Future Minimum Payments Receivable, in Two Years	615
Operating Leases, Future Minimum Payments Receivable, in Three Years	370
Operating Leases, Future Minimum Payments Receivable, in Four Years	87
Operating Leases, Future Minimum Payments Receivable, in Five Years	$ 10