Investments - Marketable Debt Securities (Details) (USD $)	12 Months Ended
	Jan. 03, 2015	Dec. 28, 2013	Dec. 29, 2012
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds	$ 54,200,000	$ 53,300,000	$ 26,000,000
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	20,000	51,000
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	75,000	30,000
Available-for-sale Debt Securities, Amortized Cost Basis	114,105,000	86,770,000
Available-for-sale Securities, Debt Securities	114,050,000	86,791,000
Amortized Cost [Abstract]
Marketable debt securities - current (due in less than one year)	69,607,000	52,122,000
Marketable debt securities - non-current (due in one to two years)	44,498,000	34,648,000
Marketable debt securities	114,105,000	86,770,000
Fair Value [Abstract]
Marketable debt securities - current (due in less than one year)	69,609,000	52,159,000
Marketable debt securities - non-current (due in one to two years)	44,441,000	34,632,000
U.S. Treasury securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	12,000	15,000
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	23,000	1,000
Available-for-sale Debt Securities, Amortized Cost Basis	32,507,000	23,975,000
Available-for-sale Securities, Debt Securities	32,496,000	23,989,000
Amortized Cost [Abstract]
Marketable debt securities	32,507,000	23,975,000
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	2,000	3,000
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	36,000	23,000
Available-for-sale Debt Securities, Amortized Cost Basis	35,409,000	35,804,000
Available-for-sale Securities, Debt Securities	35,375,000	35,784,000
Amortized Cost [Abstract]
Marketable debt securities	35,409,000	35,804,000
U.S. Agency bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	4,000	10,000
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	10,000	4,000
Available-for-sale Debt Securities, Amortized Cost Basis	22,545,000	19,517,000
Available-for-sale Securities, Debt Securities	22,539,000	19,523,000
Amortized Cost [Abstract]
Marketable debt securities	22,545,000	19,517,000
Municipal bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	2,000	23,000
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	5,000	2,000
Available-for-sale Debt Securities, Amortized Cost Basis	11,157,000	7,474,000
Available-for-sale Securities, Debt Securities	11,154,000	7,495,000
Amortized Cost [Abstract]
Marketable debt securities	11,157,000	7,474,000
Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	1,000
Available-for-sale Debt Securities, Amortized Cost Basis	12,487,000
Available-for-sale Securities, Debt Securities	12,486,000
Amortized Cost [Abstract]
Marketable debt securities	$ 12,487,000