Fair Value Measurements (Details) - Recurring [Member] - USD ($) $ in Thousands	Jul. 04, 2015	Jan. 03, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	$ 62,379	$ 69,609
Marketable debt securities - noncurrent	28,751	44,441
Marketable debt securities	91,130	114,050
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	15,012	17,506
Marketable debt securities - noncurrent	7,515	14,990
Marketable debt securities	22,527	32,496
Deferred compensation plan liability	1,300	1,000
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	47,367	52,103
Marketable debt securities - noncurrent	21,236	29,451
Marketable debt securities	68,603	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]
Marketable securities assets funding the deferred compensation plan	1,300	1,000
US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	15,012	17,506
Marketable debt securities - noncurrent	7,515	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	15,012	17,506
Marketable debt securities - noncurrent	7,515	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	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	15,059	20,139
Marketable debt securities - noncurrent	12,627	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	15,059	20,139
Marketable debt securities - noncurrent	12,627	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	15,011	12,525
Marketable debt securities - noncurrent	7,530	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	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	15,011	12,525
Marketable debt securities - noncurrent	7,530	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	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	9,804	6,953
Marketable debt securities - noncurrent	1,079	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	9,804	6,953
Marketable debt securities - noncurrent	1,079	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, Not Included with Cash and Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	7,493	12,486
Commercial Paper, Not Included with Cash and Cash Equivalents [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	0	0
Commercial Paper, Not Included with Cash and Cash Equivalents [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	7,493	12,486
Commercial Paper, Not Included with Cash and Cash Equivalents [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable debt securities - current	$ 0	$ 0