Additional Balance Sheet And Cash Flow Information (Marketable Securities) (Details) (USD $)	3 Months Ended
Apr. 01, 2012 M	Mar. 27, 2011	Dec. 31, 2011
Additional Balance Sheet And Cash Flow Information [Line Items]
Available-for-sale securities	$ 134,946,000	$ 115,209,000	$ 153,380,000
Gross unrealized gains	1,600,000	100,000
Gross unrealized gains, net of taxes	1,000,000	40,000
Contractual maturities period of marketable securities, minimum (in months)	12
Contractual maturities period of marketable securities, maximum (in months)	48
Corporate Bonds [Member]
Additional Balance Sheet And Cash Flow Information [Line Items]
Available-for-sale securities	134,946,000	55,232,000	153,380,000
U.S. Treasuries [Member]
Additional Balance Sheet And Cash Flow Information [Line Items]
Available-for-sale securities		$ 59,977,000

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