Goodwill by Reporting Segment (Details) (USD $) In Thousands, unless otherwise specified										12 Months Ended									12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Feb. 09, 2012 Ident Technology AG acquisition [Member]	Mar. 31, 2014 SMSC Acquisition [Member]	Mar. 31, 2013 SMSC Acquisition [Member]	Apr. 18, 2012 Roving Networks Acquisition [Member]	Mar. 31, 2014 Semiconductor products [Member]	Mar. 31, 2013 Semiconductor products [Member]	Mar. 31, 2012 Semiconductor products [Member]	Mar. 31, 2014 Semiconductor products [Member] Acquisition of R and E International Member	Mar. 31, 2013 Semiconductor products [Member] Acquisition of R and E International Member	Mar. 31, 2014 Semiconductor products [Member] SMSC Acquisition [Member]	Mar. 31, 2013 Semiconductor products [Member] SMSC Acquisition [Member]	Mar. 31, 2013 Semiconductor products [Member] Roving Networks Acquisition [Member]	Mar. 31, 2014 Semiconductor products [Member] Other business acquisitions [Member]	Mar. 31, 2014 Technology licensing [Member]	Mar. 31, 2013 Technology licensing [Member]	Mar. 31, 2012 Technology licensing [Member]	Mar. 31, 2014 Technology licensing [Member] Acquisition of R and E International Member	Mar. 31, 2013 Technology licensing [Member] Acquisition of R and E International Member	Mar. 31, 2014 Technology licensing [Member] SMSC Acquisition [Member]	Mar. 31, 2013 Technology licensing [Member] SMSC Acquisition [Member]	Mar. 31, 2013 Technology licensing [Member] Roving Networks Acquisition [Member]	Mar. 31, 2014 Technology licensing [Member] Other business acquisitions [Member]
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 276,097	$ 271,348	$ 17,400	$ 165,592	$ 169,065	$ 8,700	$ 256,897	$ 252,148	$ 74,313							$ 19,200	$ 19,200	$ 19,200
Additions due to business combination										111	118	(3,473)	169,065	8,652	8,111				0	0	0	0	0	0
Goodwill, ending balance	$ 276,097	$ 271,348	$ 17,400	$ 165,592	$ 169,065	$ 8,700	$ 256,897	$ 252,148	$ 74,313							$ 19,200	$ 19,200	$ 19,200