Cash, Cash Equivalents and Investments (Details) (USD $)	Oct. 01, 2011	Jan. 01, 2011
Cash, Cash Equivalents and Investments
Auction-rate securities guaranteed by the U.S. government	$ 17,300,000
Auction-rate securities privately insured	2,000,000
Auction-rate securities having credit rating 'AAA'	17,300,000
Auction-rate securities having credit rating 'A'	2,000,000
Cash on hand, Cost	41,855,000	40,644,000
Cash on hand, Fair Value	41,855,000	40,644,000
Available-for-sale securities
Cash and cash equivalents, Adjusted Cost	108,183,000	138,566,000
Cash and cash equivalents, Gross Unrealized Gains		1,000
Cash and cash equivalents, Fair Value	108,183,000	138,567,000
Money market funds \| Cash Equivalents:
Available-for-sale securities
Available-for-sale securities, Cost	66,328,000	45,167,000
Available-for-sale securities, Fair Value	66,328,000	45,167,000
Corporate bonds \| Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	80,102,000	88,183,000
Available-for-sale securities, Gross Unrealized Losses	(282,000)	(46,000)
Available-for-sale securities, Gross Unrealized Gains	240,000	381,000
Available-for-sale securities, Fair Value	80,060,000	88,518,000
U.S. government agency \| Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	10,029,000	34,635,000
Available-for-sale securities, Gross Unrealized Losses	(1,000)	(5,000)
Available-for-sale securities, Gross Unrealized Gains	20,000	50,000
Available-for-sale securities, Fair Value	10,048,000	34,680,000
U.S. Treasury bills \| Cash Equivalents:
Available-for-sale securities
Available-for-sale securities, Cost		50,096,000
Available-for-sale securities, Gross Unrealized Gains		1,000
Available-for-sale securities, Fair Value		50,097,000
U.S. Treasury bills \| Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	8,600,000	6,998,000
Available-for-sale securities, Gross Unrealized Gains		1,000
Available-for-sale securities, Fair Value	8,600,000	6,999,000
International government bonds \| Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	2,791,000	10,792,000
Available-for-sale securities, Gross Unrealized Gains	1,000	38,000
Available-for-sale securities, Fair Value	2,792,000	10,830,000
Certificates of deposit \| Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	1,570,000	5,744,000
Available-for-sale securities, Gross Unrealized Losses	(1,000)	(2,000)
Available-for-sale securities, Fair Value	1,569,000	5,742,000
Asset-backed securities \| Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	1,245,000
Available-for-sale securities, Gross Unrealized Losses	(1,000)
Available-for-sale securities, Fair Value	1,244,000
Commercial paper \| Cash Equivalents:
Available-for-sale securities
Available-for-sale securities, Cost		2,659,000
Available-for-sale securities, Fair Value		2,659,000
Commercial paper \| Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	1,000,000	2,687,000
Available-for-sale securities, Fair Value	1,000,000	2,687,000
Variable-rate demand notes \| Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	13,200,000	39,425,000
Available-for-sale securities, Fair Value	13,200,000	39,425,000
Municipal bonds \| Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	56,308,000	38,408,000
Available-for-sale securities, Gross Unrealized Losses	(5,000)	(18,000)
Available-for-sale securities, Gross Unrealized Gains	99,000	24,000
Available-for-sale securities, Fair Value	56,402,000	38,414,000
Auction rate securities \| Long-term Investments:
Available-for-sale securities
Long-term investment interest, low end of range (as a percent)	0.30%
Long-term investment interest, high end of range (as a percent)	3.10%
Available-for-sale securities, Cost	19,275,000	19,725,000
Available-for-sale securities, Gross Unrealized Losses	(1,435,000)	(2,225,000)
Available-for-sale securities, Fair Value	17,840,000	17,500,000
Cash Equivalents:
Available-for-sale securities
Available-for-sale securities, Cost		97,922,000
Available-for-sale securities, Gross Unrealized Gains		1,000
Available-for-sale securities, Fair Value		97,923,000
Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	174,845,000	226,872,000
Available-for-sale securities, Gross Unrealized Losses	(290,000)	(71,000)
Available-for-sale securities, Gross Unrealized Gains	360,000	494,000
Available-for-sale securities, Fair Value	174,915,000	227,295,000
Long-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	19,275,000	19,725,000
Available-for-sale securities, Gross Unrealized Losses	(1,435,000)	(2,225,000)
Available-for-sale securities, Fair Value	$ 17,840,000	$ 17,500,000

This element represents the amount of auction-rate securities that is guaranteed by the U.S. government.

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- Definition

This element represents the amount of auction-rate securities having credit rating of 'A'.

+ Details

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- Definition

This element represents the amount of auction-rate securities having credit rating of 'AAA'.

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- Definition

This element represents the amount of auction-rate securities that is privately insured.

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- Definition

This element represents the adjusted cost of cash and cash equivalents that are considered available-for-sale and recorded at fair value.

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- Definition

This element represents the unrealized gains from cash and cash equivalents.

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- Definition

Represents fair value of cash which is similar to carrying value of cash as of balance sheet date.

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- Definition

The high end of the range of interest rates for investments.

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- Definition

The low end of the range of interest rates for investments.

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- Definition

This item represents the cost of debt 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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- Definition

For an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading.

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

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Unrestricted cash available for day-to-day operating needs, for an entity that has cash equivalents, but does not aggregate cash equivalents with cash on the balance sheet.

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- Definition

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.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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