Cash, Cash Equivalents and Short-Term Investments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 30, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Cash, Cash Equivalents and Short-Term Investments
Cash and cash equivalents	$ 4,416	$ 9,403	$ 2,780	$ 6,211
Short-term investments	4,459	947
Commercial paper
Cash, Cash Equivalents and Short-Term Investments
Short-term investments	948	611
Corporate debt
Cash, Cash Equivalents and Short-Term Investments
Cash and cash equivalents	459
Short-term investments	3,161
Bank certificate of deposit
Cash, Cash Equivalents and Short-Term Investments
Short-term investments	350	100
Cash
Cash, Cash Equivalents and Short-Term Investments
Cash and cash equivalents	249	6,240
Money market funds
Cash, Cash Equivalents and Short-Term Investments
Cash and cash equivalents	3,708	3,163
Short-term investments		$ 236