Leased Vehicles Minimum rental payments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2013
Fiscal 2013 [Member]
Minimum Lease Payments [Line Items]
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	$ 303
Fiscal 2014 [Member]
Minimum Lease Payments [Line Items]
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	461
Fiscal 2015 [Member]
Minimum Lease Payments [Line Items]
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	342
Fiscal 2016 [Member]
Minimum Lease Payments [Line Items]
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	118
Fiscal 2017 [Member]
Minimum Lease Payments [Line Items]
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	11
Fiscal 2018 [Member]
Minimum Lease Payments [Line Items]
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	$ 1