Fair Value of Financial Instruments (Details) (Recurring, USD $) In Thousands, unless otherwise specified	Mar. 30, 2013	Dec. 31, 2012
Total
Fair Value of Financial Instruments
Total financial assets at fair value	$ 8,626	$ 4,110
Total | Money market funds
Fair Value of Financial Instruments
Total financial assets at fair value	3,708	3,399
Total | Bank certificate of deposit
Fair Value of Financial Instruments
Total financial assets at fair value	350	100
Total | Corporate debt securities
Fair Value of Financial Instruments
Total financial assets at fair value	3,620	611
Total | Commercial Paper
Fair Value of Financial Instruments
Total financial assets at fair value	948
Quoted Prices In Active Markets (Level 1)
Fair Value of Financial Instruments
Total financial assets at fair value	3,708	3,399
Quoted Prices In Active Markets (Level 1) | Money market funds
Fair Value of Financial Instruments
Total financial assets at fair value	3,708	3,399
Other Observable Inputs (Level 2)
Fair Value of Financial Instruments
Total financial assets at fair value	4,918	711
Other Observable Inputs (Level 2) | Bank certificate of deposit
Fair Value of Financial Instruments
Total financial assets at fair value	350	100
Other Observable Inputs (Level 2) | Corporate debt securities
Fair Value of Financial Instruments
Total financial assets at fair value	3,620	611
Other Observable Inputs (Level 2) | Commercial Paper
Fair Value of Financial Instruments
Total financial assets at fair value	$ 948