Marketable Debt Securities (Details) (USD $)	3 Months Ended			6 Months Ended			12 Months Ended
	Jun. 29, 2013		Jun. 30, 2012	Jun. 29, 2013		Jun. 30, 2012	Dec. 29, 2012
Schedule of Available-for-sale Securities [Line Items]
Proceeds from maturity of marketable debt securities	$ 17,500,000		$ 10,000,000	$ 23,300,000		$ 10,000,000
Investments of marketable debt securities [Abstract]
Amortized cost	82,330,000			82,330,000			89,873,000
Unrealized gains				22,000			57,000
Unrealized losses				(63,000)			(24,000)
Fair value	82,289,000	[1]		82,289,000	[1]		89,906,000	[1]
Amortized Cost [Abstract]
Marketable debt securities - current (due in less than one year)	53,798,000			53,798,000			51,238,000
Marketable debt securities - non-current (due in one to two years)	28,532,000			28,532,000			38,635,000
Marketable debt securities	82,330,000			82,330,000			89,873,000
Fair Value [Abstract]
Marketable debt securities - current (due in less than one year)	53,787,000	[1]		53,787,000	[1]		51,264,000	[1]
Marketable debt securities - non-current (due in one to two years)	28,502,000	[1]		28,502,000	[1]		38,642,000	[1]
Marketable debt securities	82,289,000	[1]		82,289,000	[1]		89,906,000	[1]
U.S. Treasury securities [Member]
Investments of marketable debt securities [Abstract]
Amortized cost	22,504,000			22,504,000			32,518,000
Unrealized gains				14,000			24,000
Unrealized losses				0			0
Fair value	22,518,000	[1]		22,518,000	[1]		32,542,000	[1]
Corporate bonds [Member]
Investments of marketable debt securities [Abstract]
Amortized cost	35,569,000			35,569,000			31,929,000
Unrealized gains				0			2,000
Unrealized losses				(57,000)			(23,000)
Fair value	35,512,000	[1]		35,512,000	[1]		31,908,000	[1]
Agency Securities [Member]
Investments of marketable debt securities [Abstract]
Amortized cost	17,544,000			17,544,000			17,632,000
Unrealized gains				7,000			11,000
Unrealized losses				(6,000)			(1,000)
Fair value	17,545,000	[1]		17,545,000	[1]		17,642,000	[1]
Municipal bonds [Member]
Investments of marketable debt securities [Abstract]
Amortized cost	6,713,000			6,713,000			7,794,000
Unrealized gains				1,000			20,000
Unrealized losses				0			0
Fair value	$ 6,714,000	[1]		$ 6,714,000	[1]		$ 7,814,000	[1]

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