Cash Equivalents and Investments (Details 1) (USD $) In Thousands, unless otherwise specified	Apr. 01, 2012	Dec. 31, 2011
Short-term debt [Member]
Company's available-for-sale securities
Available-for-sale securities, Amortized Cost	$ 154,527	$ 147,209
Available-for-sale securities, Gross Unrealized Gain	8,345	8,843
Available-for-sale securities, Gross Unrealized Loss	(458)	(408)
Available-for-sale securities, Fair Value	162,414	155,644
Asset-backed and mortgage-backed securities [Member]
Company's available-for-sale securities
Available-for-sale securities, Amortized Cost	104,656	99,884
Available-for-sale securities, Gross Unrealized Gain	7,383	7,891
Available-for-sale securities, Gross Unrealized Loss	(445)	(378)
Available-for-sale securities, Fair Value	111,594	107,397
U.S. government and agency securities [Member]
Company's available-for-sale securities
Available-for-sale securities, Amortized Cost	39,262	35,179
Available-for-sale securities, Gross Unrealized Gain	794	799
Available-for-sale securities, Gross Unrealized Loss	(12)	(3)
Available-for-sale securities, Fair Value	40,044	35,975
Corporate debt securities [Member]
Company's available-for-sale securities
Available-for-sale securities, Amortized Cost	10,609	12,146
Available-for-sale securities, Gross Unrealized Gain	168	153
Available-for-sale securities, Gross Unrealized Loss	(1)	(27)
Available-for-sale securities, Fair Value	10,776	12,272
Long-term marketable equity securities [Member]
Company's available-for-sale securities
Available-for-sale equity securities, Amortized Cost	669	669
Available-for-sale securities, Gross Unrealized Gain	1,173	846
Available-for-sale securities, Gross Unrealized Loss	(1)	(1)
Available-for-sale securities, Fair Value	$ 1,841	$ 1,514

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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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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