Segment Information (Net Revenue By Geographic Area) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2010
Revenue from External Customer [Line Items]
Net revenue	$ 1,061	$ 1,053	$ 2,775	$ 2,499
North America [Member]
Revenue from External Customer [Line Items]
Net revenue from unaffiliated customers	500	528	1,338	1,306
Europe [Member]
Revenue from External Customer [Line Items]
Net revenue from unaffiliated customers	505	477	1,271	1,056
Asia [Member]
Revenue from External Customer [Line Items]
Net revenue from unaffiliated customers	$ 56	$ 48	$ 166	$ 137