Investments - Marketable Debt Securities (Details) (USD $)	12 Months Ended
	Dec. 28, 2013		Dec. 29, 2012		Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	$ 86,770,000		$ 89,873,000
Available-for-sale Securities, Debt Securities	86,791,000	[1]	89,906,000	[1]
Available For Sale Debt Securities Gross Unrealized Losses	30,000		24,000
Available for Sale Debt Securities Gross Unrealized Gains	51,000		57,000
Proceeds From Sale Of Available For Sale Debt Securities	53,300,000		26,000,000		10,000,000
Amortized Cost [Abstract]
Marketable debt securities - current (due in less than one year)	52,122,000		51,238,000
Marketable debt securities - non-current (due in one to two years)	34,648,000		38,635,000
Marketable debt securities	86,770,000		89,873,000
Fair Value [Abstract]
Marketable debt securities - current (due in less than one year)	52,159,000	[1]	51,264,000	[1]
Marketable debt securities - non-current (due in one to two years)	34,632,000	[1]	38,642,000	[1]
Marketable debt securities	86,791,000	[1]	89,906,000	[1]
U.S. Treasury securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	23,975,000		32,518,000
Available-for-sale Securities, Debt Securities	23,989,000	[1]	32,542,000	[1]
Available For Sale Debt Securities Gross Unrealized Losses	1,000		0
Available for Sale Debt Securities Gross Unrealized Gains	15,000		24,000
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	35,804,000		31,929,000
Available-for-sale Securities, Debt Securities	35,784,000	[1]	31,908,000	[1]
Available For Sale Debt Securities Gross Unrealized Losses	23,000		23,000
Available for Sale Debt Securities Gross Unrealized Gains	3,000		2,000
U.S. Agency bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	19,517,000		17,632,000
Available-for-sale Securities, Debt Securities	19,523,000		17,642,000	[1]
Available For Sale Debt Securities Gross Unrealized Losses	4,000		1,000
Available for Sale Debt Securities Gross Unrealized Gains	10,000		11,000
Municipal bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	7,474,000		7,794,000
Available-for-sale Securities, Debt Securities	7,495,000	[1]	7,814,000	[1]
Available For Sale Debt Securities Gross Unrealized Losses	2,000		0
Available for Sale Debt Securities Gross Unrealized Gains	$ 23,000		$ 20,000

[1] See Note 2 for discussion of fair value measurements.