Investments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 29, 2012	Mar. 31, 2012
Available for sale Securities Current
Schedule of Available-for-sale Securities
Cost	$ 105,325	$ 147,925
Unrealized Gain	27	56
Fair Value	105,352	147,981
Available for sale Securities Current \| Commercial Paper
Schedule of Available-for-sale Securities
Cost	44,265	83,645
Unrealized Gain	1
Fair Value	44,266	83,645
Available for sale Securities Current \| Government agencies
Schedule of Available-for-sale Securities
Cost	43,185	46,293
Unrealized Gain	14	5
Fair Value	43,199	46,298
Available for sale Securities Current \| Corporate Bonds
Schedule of Available-for-sale Securities
Cost	16,827	17,987
Unrealized Gain	12	51
Fair Value	16,839	18,038
Available for sale Securities Current \| Municipal Bonds
Schedule of Available-for-sale Securities
Cost	1,048
Fair Value	1,048
Available for sale Securities Non Current
Schedule of Available-for-sale Securities
Cost	6,249	23,059
Unrealized Gain	4	13
Unrealized Loss		(26)
Fair Value	6,253	23,046
Available for sale Securities Non Current \| Government agencies
Schedule of Available-for-sale Securities
Cost	4,997	20,989
Unrealized Gain	4
Unrealized Loss		(26)
Fair Value	5,001	20,963
Available for sale Securities Non Current \| Corporate Bonds
Schedule of Available-for-sale Securities
Cost	1,252	2,070
Unrealized Gain		13
Fair Value	$ 1,252	$ 2,083

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

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