Cash and Investments (Details) (USD $) In Thousands, unless otherwise specified	Sep. 27, 2014	Dec. 28, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 84,371	$ 92,853
Gross Unrealized Gains	19	22
Gross Unrealized Losses	(17)	(13)
Estimated Fair Market Value	84,373	92,862
Cash and Cash equivalents [Member] | Cash [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	34,426	43,139
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	34,426	43,139
Cash and Cash equivalents [Member] | Money market funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	549	876
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	549	876
Cash and Cash equivalents [Member] | Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	650	750
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	650	750
Short-term investments [Member] | Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	700
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Estimated Fair Market Value	700
Short-term investments [Member] | U.S. Treasury securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,497	5,036
Gross Unrealized Gains	1	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	2,498	5,036
Short-term investments [Member] | U.S. Government agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	18,685	11,980
Gross Unrealized Gains	6	4
Gross Unrealized Losses	(4)	(4)
Estimated Fair Market Value	18,687	11,980
Short-term investments [Member] | Municipal securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,014	9,756
Gross Unrealized Gains	3	11
Gross Unrealized Losses	(2)	(4)
Estimated Fair Market Value	5,015	9,763
Short-term investments [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	21,850	21,316
Gross Unrealized Gains	9	7
Gross Unrealized Losses	(11)	(5)
Estimated Fair Market Value	$ 21,848	$ 21,318