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Amortized Cost and Fair Value of Available-for-Sale Investments (Detail) - USD ($) $ in Thousands | Sep. 28, 2019 | Dec. 29, 2018
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 115,551 | $ 113,359
Gross Unrealized Gains | 1,536 | 33
Gross Unrealized Losses | 31 | 1,217
Fair Value | 117,056 | 112,175
Money market investments |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 14,923 | 11,714
Fair Value | 14,923 | 11,714
Asset-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 590 | 624
Gross Unrealized Gains | 2 |
Gross Unrealized Losses |  | 4
Fair Value | 592 | 620
Corporate bonds and direct obligations of government agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 97,704 | 101,021
Gross Unrealized Gains | 1,513 | 33
Gross Unrealized Losses | 31 | 1,213
Fair Value | 99,186 | $ 99,841
U.S. Treasury obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 2,334 |
Gross Unrealized Gains | 21 |
Fair Value | $ 2,355 |

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- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454 + Details
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- Definition Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
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