Segment Information (Net Revenue By Geographic Area) (Details) (USD $) In Millions	3 Months Ended	6 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Revenue from External Customer [Line Items]
Net revenue	$ 715	$ 631	$ 1,714	$ 1,446
North America [Member]
Revenue from External Customer [Line Items]
Net revenue from unaffiliated customers	337	327	838	778
Europe [Member]
Revenue from External Customer [Line Items]
Net revenue from unaffiliated customers	328	262	766	579
Asia [Member]
Revenue from External Customer [Line Items]
Net revenue from unaffiliated customers	$ 50	$ 42	$ 110	$ 89

Revenues from external customers attributed to all foreign countries in total from which the entity derives revenues.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 131

-Paragraph 38

-Subparagraph a(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 280

-SubTopic 10

-Section 50

-Paragraph 41

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e9038-108599

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration