Fair Value Measurements (Details) (Recurring [Member], USD $)	Dec. 28, 2013	Dec. 29, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	$ 52,159,000	$ 51,264,000
Marketable debt securities - noncurrent	34,632,000	38,642,000
Marketable debt securities	86,791,000	89,906,000
Deferred compensation plan liability	1,100,000	1,600,000
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	15,011,000	17,538,000
Marketable debt securities - noncurrent	8,978,000	15,004,000
Marketable debt securities	23,989,000	32,542,000
Marketable securities assets funding the deferred compensation plan	1,100,000	1,600,000
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	37,148,000	33,726,000
Marketable debt securities - noncurrent	25,654,000	23,638,000
Marketable debt securities	62,802,000	57,364,000
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	0	0
Marketable debt securities - noncurrent	0	0
Marketable debt securities	0	0
US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	15,011,000	17,538,000
Marketable debt securities - noncurrent	8,978,000	15,004,000
US Treasury Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	15,011,000	17,538,000
Marketable debt securities - noncurrent	8,978,000	15,004,000
US Treasury Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	0	0
Marketable debt securities - noncurrent	0	0
US Treasury Securities [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	0	0
Marketable debt securities - noncurrent	0	0
Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	20,300,000	21,549,000
Marketable debt securities - noncurrent	15,484,000	10,359,000
Corporate Bonds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	0	0
Marketable debt securities - noncurrent	0	0
Corporate Bonds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	20,300,000	21,549,000
Marketable debt securities - noncurrent	15,484,000	10,359,000
Corporate Bonds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	0	0
Marketable debt securities - noncurrent	0	0
U.S. Agency bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	12,025,000	7,586,000
Marketable debt securities - noncurrent	7,498,000	10,056,000
U.S. Agency bonds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	0	0
Marketable debt securities - noncurrent	0	0
U.S. Agency bonds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	12,025,000	7,586,000
Marketable debt securities - noncurrent	7,498,000	10,056,000
U.S. Agency bonds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	0	0
Marketable debt securities - noncurrent	0	0
Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	4,823,000	4,591,000
Marketable debt securities - noncurrent	2,672,000	3,223,000
Municipal Bonds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	0	0
Marketable debt securities - noncurrent	0	0
Municipal Bonds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	4,823,000	4,591,000
Marketable debt securities - noncurrent	2,672,000	3,223,000
Municipal Bonds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	0	0
Marketable debt securities - noncurrent	$ 0	$ 0