Investments in Cash Equivalents and Marketable Securities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended	12 Months Ended
Oct. 01, 2011	Oct. 01, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 124,647	$ 124,647	$ 151,232
Available For Sale Securities Net Unrealized Gains		2	4
Available For Sale Securities Net Unrealized Losses		(4)	(2)
Available-for-sale Securities	124,645	124,645	151,234
Available-for-sale Securities, Other Disclosure Items [Abstract]
Maximum Term Of Available For Sale Securities	1	1	1
Marketable Securities, Realized Loss, Other than Temporary Impairments, Amount	0	0
Cash Equivalents [Member] \| Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	29,273	29,273
Available For Sale Securities Net Unrealized Gains		0
Available For Sale Securities Net Unrealized Losses		0
Available-for-sale Securities	29,273	29,273
Cash Equivalents [Member] \| Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	46,930	46,930	114,217
Available For Sale Securities Net Unrealized Gains		0	0
Available For Sale Securities Net Unrealized Losses		0	0
Available-for-sale Securities	46,930	46,930	114,217
Cash Equivalents [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	10,900	10,900
Available For Sale Securities Net Unrealized Gains		0
Available For Sale Securities Net Unrealized Losses		2
Available-for-sale Securities	10,898	10,898
Cash Equivalents [Member] \| US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	4,000	4,000	5,500
Available For Sale Securities Net Unrealized Gains		0	0
Available For Sale Securities Net Unrealized Losses		0	0
Available-for-sale Securities	4,000	4,000	5,500
Cash Equivalents [Member] \| Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis			325
Available For Sale Securities Net Unrealized Gains			0
Available For Sale Securities Net Unrealized Losses			0
Available-for-sale Securities			325
Short Term Marketable Securities [Member] \| Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	8,018	8,018
Available For Sale Securities Net Unrealized Gains		0
Available For Sale Securities Net Unrealized Losses		(1)
Available-for-sale Securities	8,017	8,017
Short Term Marketable Securities [Member] \| Municipal Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	9,295	9,295
Available For Sale Securities Net Unrealized Gains		0
Available For Sale Securities Net Unrealized Losses		0
Available-for-sale Securities	9,295	9,295
Short Term Marketable Securities [Member] \| US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	10,001	10,001	26,366
Available For Sale Securities Net Unrealized Gains		0	4
Available For Sale Securities Net Unrealized Losses		(1)	0
Available-for-sale Securities	10,000	10,000	26,370
Short Term Marketable Securities [Member] \| US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	6,024	6,024	3,115
Available For Sale Securities Net Unrealized Gains		2	0
Available For Sale Securities Net Unrealized Losses		0	(2)
Available-for-sale Securities	6,026	6,026	3,113
Short Term Marketable Securities [Member] \| Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	206	206	1,709
Available For Sale Securities Net Unrealized Gains		0	0
Available For Sale Securities Net Unrealized Losses		0	0
Available-for-sale Securities	$ 206	$ 206	$ 1,709

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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-Publisher FASB

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-Number 115

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Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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+ Details