Fair Value Measurements (Details) - Recurring [Member] - USD ($) $ in Thousands	Jan. 02, 2016	Jan. 03, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	$ 6,567	$ 69,609
Marketable debt securities - noncurrent	8,553	44,441
Marketable debt securities	15,120	114,050
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	0	17,506
Marketable debt securities - noncurrent	0	14,990
Marketable debt securities	0	32,496
Deferred compensation plan liability	1,600	1,000
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	6,567	52,103
Marketable debt securities - noncurrent	8,553	29,451
Marketable debt securities	15,120	81,554
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
Available-for-sale Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred Compensation Plan Assets	1,600	1,000
US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current		17,506
Marketable debt securities - noncurrent		14,990
US Treasury Securities [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current		17,506
Marketable debt securities - noncurrent		14,990
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
Marketable debt securities - noncurrent		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
Marketable debt securities - noncurrent		0
Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	2,512	20,139
Marketable debt securities - noncurrent	5,001	15,236
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	2,512	20,139
Marketable debt securities - noncurrent	5,001	15,236
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		12,525
Marketable debt securities - noncurrent	2,496	10,014
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
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		12,525
Marketable debt securities - noncurrent	2,496	10,014
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
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	4,055	6,953
Marketable debt securities - noncurrent	1,056	4,201
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	4,055	6,953
Marketable debt securities - noncurrent	1,056	4,201
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
Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current		12,486
Commercial Paper [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current		0
Commercial Paper [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current		12,486
Commercial Paper [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current		$ 0