Fair Value Measurement (Details) (Measured on a Recurring Basis [Member], USD $) In Thousands, unless otherwise specified	Dec. 29, 2013	Mar. 31, 2013
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Cash Equivalents and Short-Term Investments:
US government treasuries and agencies securities	$ 120,594	$ 87,379
Money market funds	65,587	79,083
Corporate bonds	0	0
International government bonds	0	0
Bank deposits	0	0
Municipal bonds	0	0
Total assets measured at fair value	186,181	166,462
Liabilities:
Fair value of long term contingent consideration	0	0
Total liabilities measured at fair value	0	0
Significant Other Observable Inputs (Level 2) [Member]
Cash Equivalents and Short-Term Investments:
US government treasuries and agencies securities	0	0
Money market funds	0	0
Asset-backed Securities Fair Value Disclosure	16,128	9,855
Corporate bonds	173,243	58,716
International government bonds	3,023	3,066
Bank deposits	17,205	16,583
Municipal bonds	8,174	2,094
Total assets measured at fair value	217,773	90,314
Liabilities:
Fair value of long term contingent consideration	0	0
Total liabilities measured at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member]
Cash Equivalents and Short-Term Investments:
US government treasuries and agencies securities	0	0
Money market funds	0	0
Corporate bonds	0	0
International government bonds	0	0
Bank deposits	0	0
Municipal bonds	0	0
Total assets measured at fair value	0	0
Liabilities:
Fair value of long term contingent consideration		6,695
Total liabilities measured at fair value	1,880	6,695
Estimate of Fair Value, Fair Value Disclosure [Member]
Cash Equivalents and Short-Term Investments:
US government treasuries and agencies securities	120,594	87,379
Money market funds	65,587	79,083
Asset-backed Securities Fair Value Disclosure	16,128	9,855
Corporate bonds	173,243	58,716
International government bonds	3,023	3,066
Bank deposits	17,205	16,583
Municipal bonds	8,174	2,094
Total assets measured at fair value	403,954	256,776
Liabilities:
Fair value of long term contingent consideration	1,880	6,695
Total liabilities measured at fair value	$ 1,880	$ 6,695