Cash, Cash Equivalents and Investments (Details 2) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 28, 2014	Dec. 28, 2013
Short-term investments
Amortized Cost	$ 96,968	$ 96,462
Gross Unrealized Gains	956	339
Gross Unrealized Losses	(14)	(13)
Fair Value	97,910	96,788
Corporate debt securities [Member]
Short-term investments
Amortized Cost	36,615	37,422
Gross Unrealized Gains	23	30
Gross Unrealized Losses	(13)	(11)
Fair Value	36,625	37,441
Bank certificates of deposit [Member]
Short-term investments
Amortized Cost	24,249	20,300
Gross Unrealized Gains	10	9
Gross Unrealized Losses	0	(1)
Fair Value	24,259	20,308
United States Treasury securities [Member]
Short-term investments
Amortized Cost	19,273	24,219
Gross Unrealized Gains	37	28
Gross Unrealized Losses	0	(1)
Fair Value	19,310	24,246
United States government agency securities [Member]
Short-term investments
Amortized Cost	11,352	10,212
Gross Unrealized Gains	10	11
Gross Unrealized Losses	(1)	0
Fair Value	11,361	10,223
Commercial paper [Member]
Short-term investments
Amortized Cost	1,994	2,492
Gross Unrealized Gains	1	1
Gross Unrealized Losses	0	0
Fair Value	1,995	2,493
Marketable debt securities [Member]
Short-term investments
Amortized Cost	93,483	94,645
Gross Unrealized Gains	81	79
Gross Unrealized Losses	(14)	(13)
Fair Value	93,550	94,711
Marketable equity securities [Member]
Short-term investments
Amortized Cost	3,485	1,817
Gross Unrealized Gains	875	260
Gross Unrealized Losses	0	0
Fair Value	$ 4,360	$ 2,077