Goodwill and Acquisition-Related Intangibles (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Dec. 31, 2011	Apr. 02, 2011
Gross and net amounts of goodwill and of acquisition-related intangibles
Goodwill	$ 149,701	$ 133,580	[1]
In-process research and development	4,000	6,000
Total acquisition-related intangibles, gross	126,646	109,640
Less accumulated amortization	(88,332)	(82,744)
Total acquisition-related intangibles, net	38,314	26,896
Core Technology [Member]
Gross and net amounts of goodwill and of acquisition-related intangibles
Total acquisition-related intangibles, gross	76,440	58,439
Less accumulated amortization	(44,401)	(39,789)
Total acquisition-related intangibles, net	32,039	18,650
Weighted Average Amortization Life	5.7
Other Intangibles [Member]
Gross and net amounts of goodwill and of acquisition-related intangibles
Total acquisition-related intangibles, gross	46,206	45,201
Less accumulated amortization	(43,931)	(42,955)
Total acquisition-related intangibles, net	$ 2,275	$ 2,246
Weighted Average Amortization Life	2.7

[1] Derived from audited financial statements