Cash, Cash Equivalents and Investments (Details 2) (USD $)	3 Months Ended	6 Months Ended
Jul. 03, 2011	Jul. 03, 2011
Effective maturity dates of available-for-sale investments
Less than 1 Year	$ 202,012,000	$ 202,012,000
1-2 Years	68,634,000	68,634,000
2-3 Years	33,117,000	33,117,000
3-4 Years	1,016,000	1,016,000
Fair Value, Total	304,779,000	304,779,000
Schedule of Available-for-Sale Securities (Textuals) [Abstract]
Other-than-temporary impairment		0
Gross realized gains on sale of debt securities	22,000	31,000
Gross realized losses on sale of debt securities	3,000	17,000
Maximum amount committed to invest in limited partnership		20,500,000
Contribution to limited partnership	19,886,000	19,886,000
Remaining amount of commitment in limited partnership	614,000	614,000
Treasury bills [Member]
Effective maturity dates of available-for-sale investments
Less than 1 Year	12,979,000	12,979,000
1-2 Years	691,000	691,000
2-3 Years	0	0
3-4 Years	0	0
Fair Value, Total	13,670,000	13,670,000
Municipal bonds [Member]
Effective maturity dates of available-for-sale investments
Less than 1 Year	86,029,000	86,029,000
1-2 Years	23,889,000	23,889,000
2-3 Years	7,769,000	7,769,000
3-4 Years	1,016,000	1,016,000
Fair Value, Total	118,703,000	118,703,000
Corporate bonds [Member]
Effective maturity dates of available-for-sale investments
Less than 1 Year	68,425,000	68,425,000
1-2 Years	20,879,000	20,879,000
2-3 Years	16,440,000	16,440,000
3-4 Years	0	0
Fair Value, Total	105,744,000	105,744,000
Agency bonds [Member]
Effective maturity dates of available-for-sale investments
Less than 1 Year	23,428,000	23,428,000
1-2 Years	11,984,000	11,984,000
2-3 Years	3,004,000	3,004,000
3-4 Years	0	0
Fair Value, Total	38,416,000	38,416,000
Sovereign bonds [Member]
Effective maturity dates of available-for-sale investments
Less than 1 Year	11,151,000	11,151,000
1-2 Years	4,476,000	4,476,000
2-3 Years	5,904,000	5,904,000
3-4 Years	0	0
Fair Value, Total	21,531,000	21,531,000
Covered bonds [Member]
Effective maturity dates of available-for-sale investments
Less than 1 Year	0	0
1-2 Years	6,715,000	6,715,000
2-3 Years	0	0
3-4 Years	0	0
Fair Value, Total	$ 6,715,000	$ 6,715,000

Available-for-sale securities, debt maturities after one year but before second year, fair value.

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Contribution to limited partnership.

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Schedule Of Available For Sale Securities.

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This item represents the fair value of debt securities which are expected to mature within one year of the balance sheet date and which are categorized neither as held-to-maturity nor trading securities.

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For an unclassified balance sheet, total of debt securities categorized neither as held-to-maturity nor trading.

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The amount by which the fair value of an investment in debt and equity securities categorized as Available-for-sale is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

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