Leases (Narrative) (Details) (Details) - USD ($) $ in Millions	12 Months Ended
Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Leases [Abstract]
Operating leases, rent expense net	$ 130	$ 121	$ 110
Guaranteed residual value of fleet leases	$ 32
Residual value as percentage of original cost	9.80%

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

Name:	us-gaap_GuaranteeObligationsMaximumExposure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant