Leases Leases (Narrative) (Details) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Leases [Abstract]
Operating leases, rent expense net	$ 110	$ 106	$ 102
Capital lease obligations and the related capital assets are not material	Outstanding capital lease obligations and the related capital assets are not material	Outstanding capital lease obligations and the related capital assets are not material
Guaranteed residual value of fleet leases	$ 25
Residual value as percentage of original cost	10.20%