Business Acquisitions (Details) (USD $)	12 Months Ended		12 Months Ended					12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2011 Other non material business acquisitions [Member]	Mar. 31, 2010 Other non material business acquisitions [Member]	Mar. 31, 2010 Other non material business acquisitions [Member] In-process research and development [Member]	Feb. 09, 2012 Ident Technology AG acquisition [Member]	Feb. 09, 2012 Ident Technology AG acquisition [Member] In-process research and development [Member]	Mar. 31, 2011 Silicon Storage Technology, Inc. acquisition [Member]	Apr. 08, 2010 Silicon Storage Technology, Inc. acquisition [Member]	Apr. 08, 2010 Silicon Storage Technology, Inc. acquisition [Member] Semiconductor products [Member]	Apr. 08, 2010 Silicon Storage Technology, Inc. acquisition [Member] Technology licensing [Member]	Apr. 08, 2010 Silicon Storage Technology, Inc. acquisition [Member] Core/developed technology [Member]	Apr. 08, 2010 Silicon Storage Technology, Inc. acquisition [Member] In-process research and development [Member]	Apr. 08, 2010 Silicon Storage Technology, Inc. acquisition [Member] Trademarks and trade names [Member]	Apr. 08, 2010 Silicon Storage Technology, Inc. acquisition [Member] Customer-related [Member]	Apr. 08, 2010 Silicon Storage Technology, Inc. acquisition [Member] Backlog [Member]
Business Acquisition, Cost of Acquired Entity, Purchase Price [Abstract]
Price per share at fair value (in amount per share)									$ 3.05
Total consideration				$ 9,300,000		$ 39,500,000			$ 353,800,000
Total cash consideration paid									295,400,000
Cost to acquire company, cash paid, net of cash acquired			6,500,000
Total equity consideration paid									58,400,000
Assets acquired [Abstract]
Cash and cash equivalents			2,500,000
Goodwill			1,000,000	4,200,000		17,400,000			25,000,000	5,800,000	19,200,000
Purchased intangible assets			5,600,000	7,000,000	2,900,000	18,100,000	8,200,000		50,900,000			32,900,000	900,000	1,700,000	13,100,000	2,300,000
Liabilities assumed [Abstract]
Bankruptcy reorganization liability	0	19,385,000	19,400,000
Contingent consideration			$ 2,000,000	$ 1,300,000
Acquired Finite-lived Intangible Asset, Weighted Average Useful Life			7	7
Useful life minimum	1							5
Useful life maximum	10							10