Goodwill and Intangible Assets, Net (Details 1) (USD $)	3 Months Ended		6 Months Ended
	Sep. 30, 2012	Oct. 02, 2011	Sep. 30, 2012	Oct. 02, 2011	Apr. 01, 2012
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Amortization Expense	$ 5,600,000	$ 3,900,000	$ 10,500,000	$ 8,100,000
Gross assets	384,907,000		384,907,000		356,308,000
Accumulated amortization	(326,226,000)		(326,226,000)		(315,760,000)
Net assets	58,681,000		58,681,000		40,548,000
Estimated amortization expense [Abstract]
2013 (Remaining 6 months)	9,162,000
2014	16,816,000
2015	13,086,000
2016	8,071,000
2017 and thereafter	7,213,000
Total	54,348,000
Existing Technology [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross assets	240,033,000		240,033,000		223,733,000
Accumulated amortization	(197,245,000)		(197,245,000)		(192,105,000)
Net assets	42,788,000		42,788,000		31,628,000
Trademarks [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross assets	4,411,000		4,411,000		2,911,000
Accumulated amortization	(1,560,000)		(1,560,000)		(1,144,000)
Net assets	2,851,000		2,851,000		1,767,000
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross assets	131,930,000		131,930,000		127,231,000
Accumulated amortization	(126,339,000)		(126,339,000)		(122,511,000)
Net assets	5,591,000		5,591,000		4,720,000
Other Intangible Assets [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross assets	4,200,000		4,200,000
Accumulated amortization	(1,082,000)		(1,082,000)
Net assets	3,118,000		3,118,000
Subtotal [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross assets	380,574,000		380,574,000		353,875,000
Accumulated amortization	(326,226,000)		(326,226,000)		(315,760,000)
Net assets	54,348,000		54,348,000		38,115,000
In Process Research and Development [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross assets	4,333,000		4,333,000		2,433,000
Accumulated amortization	0		0		0
Net assets	$ 4,333,000		$ 4,333,000		$ 2,433,000
Minimum [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	12 months
Maximum [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	7 years