Additional Balance Sheet And Cash Flow Information (Marketable Securities) (Details) (USD $)	9 Months Ended
Sep. 25, 2011	Sep. 26, 2010	Dec. 31, 2010
Additional Balance Sheet And Cash Flow Information [Line Items]
Available-for-sale Securities	$ 179,285,000	$ 55,229,000	$ 140,118,000
Gross unrealized gains (loss)	1,500,000	(1,100,000)
Gross unrealized gains, net of taxes	900,000	(700,000)
U.S. Treasuries [Member]
Additional Balance Sheet And Cash Flow Information [Line Items]
Available-for-sale Securities			89,887,000
All Other Corporate Bonds [Member]
Additional Balance Sheet And Cash Flow Information [Line Items]
Available-for-sale Securities	$ 179,285,000	$ 55,229,000	$ 50,231,000

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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+ Details