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 includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

+ References+ Details

Cash Equivalents and Investments (Details) (Fair Value, Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	Apr. 01, 2012	Dec. 31, 2011
Company's cash equivalents and investments measured at fair value
Cash equivalents measured at fair value	$ 372,361
Investments measured at fair value	162,414	155,644
Money-market funds [Member]
Company's cash equivalents and investments measured at fair value
Cash equivalents measured at fair value	367,076	674,219
Agency securities [Member]
Company's cash equivalents and investments measured at fair value
Investments measured at fair value	103,410	97,408
Non-agency securities [Member]
Company's cash equivalents and investments measured at fair value
Investments measured at fair value	8,184	9,989
U.S. government and agency securities [Member]
Company's cash equivalents and investments measured at fair value
Cash equivalents measured at fair value	5,285
Investments measured at fair value	40,044	35,975
Corporate debt securities [Member]
Company's cash equivalents and investments measured at fair value
Investments measured at fair value	10,776	12,272
Long-term marketable equity securities [Member]
Company's cash equivalents and investments measured at fair value
Investments measured at fair value	1,841	1,514
Level 1 [Member]
Company's cash equivalents and investments measured at fair value
Cash equivalents measured at fair value	367,076
Investments measured at fair value	9,390	5,403
Level 1 [Member] \| Money-market funds [Member]
Company's cash equivalents and investments measured at fair value
Cash equivalents measured at fair value	367,076	674,219
Level 1 [Member] \| U.S. government and agency securities [Member]
Company's cash equivalents and investments measured at fair value
Investments measured at fair value	9,390	5,403
Level 1 [Member] \| Long-term marketable equity securities [Member]
Company's cash equivalents and investments measured at fair value
Investments measured at fair value	1,841	1,514
Level 2 [Member]
Company's cash equivalents and investments measured at fair value
Cash equivalents measured at fair value	5,285
Investments measured at fair value	153,024	150,241
Level 2 [Member] \| Agency securities [Member]
Company's cash equivalents and investments measured at fair value
Investments measured at fair value	103,410	97,408
Level 2 [Member] \| Non-agency securities [Member]
Company's cash equivalents and investments measured at fair value
Investments measured at fair value	8,184	9,989
Level 2 [Member] \| U.S. government and agency securities [Member]
Company's cash equivalents and investments measured at fair value
Cash equivalents measured at fair value	5,285
Investments measured at fair value	30,654	30,572
Level 2 [Member] \| Corporate debt securities [Member]
Company's cash equivalents and investments measured at fair value
Investments measured at fair value	10,776	12,272
Level 3 [Member]
Company's cash equivalents and investments measured at fair value
Cash equivalents measured at fair value
Investments measured at fair value
Level 3 [Member] \| Money-market funds [Member]
Company's cash equivalents and investments measured at fair value
Cash equivalents measured at fair value
Level 3 [Member] \| Agency securities [Member]
Company's cash equivalents and investments measured at fair value
Investments measured at fair value
Level 3 [Member] \| Non-agency securities [Member]
Company's cash equivalents and investments measured at fair value
Investments measured at fair value
Level 3 [Member] \| U.S. government and agency securities [Member]
Company's cash equivalents and investments measured at fair value
Cash equivalents measured at fair value
Investments measured at fair value
Level 3 [Member] \| Corporate debt securities [Member]
Company's cash equivalents and investments measured at fair value
Investments measured at fair value
Level 3 [Member] \| Long-term marketable equity securities [Member]
Company's cash equivalents and investments measured at fair value
Investments measured at fair value