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Amortized Cost and Fair Value of Available-for-Sale Investments (Detail) - USD ($) $ in Thousands | Dec. 30, 2017 | Dec. 31, 2016
--- | --- | ---
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | $ 111,142 | $ 109,528
Gross Unrealized Gains | 117 | 155
Gross Unrealized Losses | 340 | 264
Fair Value | 110,919 | 109,419
Money market investments |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 27,895 | 12,395
Fair Value | 27,895 | 12,395
Asset-backed securities |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 2,805 | 4,027
Gross Unrealized Gains |  | 3
Gross Unrealized Losses | 5 | 19
Fair Value | 2,800 | 4,011
Corporate bonds and direct obligations of government agencies |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 80,442 | 70,069
Gross Unrealized Gains | 117 | 150
Gross Unrealized Losses | 335 | 239
Fair Value | $ 80,224 | 69,980
U.S. Treasury obligations |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost |  | 23,037
Gross Unrealized Gains |  | 2
Gross Unrealized Losses |  | 6
Fair Value |  | $ 23,033

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- Definition This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + 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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 + Details
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