Fair Value Measurement (Details) (Measured on a Recurring Basis [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Apr. 01, 2012
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Cash Equivalents and Short-Term Investments:
US government treasuries and agencies securities	$ 145,836	$ 156,315
Money market funds	61,841	104,596
Corporate bonds	0	0
International government bonds	0	0
Corporate commercial paper	0	0
Bank deposits	0	0
Municipal bonds		0
Total assets measured at fair value	207,677	260,911
Liabilities:
Fair value of long term contingent consideration	0
Total liabilities measured at fair value	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
Corporate bonds	13,696	21,538
International government bonds	4,605	4,648
Corporate commercial paper	1,000	3,148
Bank deposits	11,441	11,633
Municipal bonds		653
Total assets measured at fair value	30,742	41,620
Liabilities:
Fair value of long term contingent consideration	0
Total liabilities measured at fair value	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
Corporate commercial paper	0	0
Bank deposits	0	0
Municipal bonds		0
Total assets measured at fair value	0	0
Liabilities:
Fair value of long term contingent consideration	6,000
Total liabilities measured at fair value	6,000
Estimate of Fair Value, Fair Value Disclosure [Member]
Cash Equivalents and Short-Term Investments:
US government treasuries and agencies securities	145,836	156,315
Money market funds	61,841	104,596
Corporate bonds	13,696	21,538
International government bonds	4,605	4,648
Corporate commercial paper	1,000	3,148
Bank deposits	11,441	11,633
Municipal bonds		653
Total assets measured at fair value	238,419	302,531
Liabilities:
Fair value of long term contingent consideration	6,000
Total liabilities measured at fair value	$ 6,000