Description Of Business And Summary Of Significant Accounting Policies (Reclassifications) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Reclassifications [Line Items]
Research and development	$ 1,153	$ 1,180	$ 1,124
Marketing and sales	788	883	781
General and administrative	354	377	296
Research and development
Reclassifications [Line Items]
Prior period reclassification adjustment		(32)	(29)
Marketing and sales
Reclassifications [Line Items]
Prior period reclassification adjustment		30	34
General and administrative
Reclassifications [Line Items]
Prior period reclassification adjustment		2	(5)
As previously reported
Reclassifications [Line Items]
Research and development		1,212	1,153
Marketing and sales		853	747
General and administrative		375	301
Reclassified balance
Reclassifications [Line Items]
Research and development		1,180	1,124
Marketing and sales		883	781
General and administrative		$ 377	$ 296