Cash and Investments (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 27, 2015	Dec. 27, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 74,797	$ 84,012
Gross Unrealized Gains	8	3
Gross Unrealized Losses	(16)	(53)
Estimated Fair Market Value	$ 74,789	$ 83,962
Investment maturity period, less than	2 years	2 years
Cash [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 24,722	$ 34,066
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	24,722	34,066
Money market funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,699	610
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	1,699	610
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,799	805
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	1,799	805
U.S. Treasury securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,499	2,498
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	(1)
Estimated Fair Market Value	2,499	2,497
U.S. Government agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,030	20,556
Gross Unrealized Gains	5	1
Gross Unrealized Losses	(3)	(19)
Estimated Fair Market Value	20,032	20,538
Municipal securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,729	3,755
Gross Unrealized Gains	2	1
Gross Unrealized Losses	(1)	(7)
Estimated Fair Market Value	3,730	3,749
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,319	21,722
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(12)	(26)
Estimated Fair Market Value	$ 20,308	$ 21,697