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 |