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Amortized Cost and Fair Value of Available for Sale Investments (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 26, 2015
--- | --- | ---
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | $ 109,528 | $ 108,229
Gross Unrealized Gains | 155 | 196
Gross Unrealized Losses | 264 | 341
Fair Value | 109,419 | 108,084
Money market investments |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 12,395 | 7,594
Fair Value | 12,395 | 7,594
Asset-backed securities |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 4,027 | 4,523
Gross Unrealized Gains | 3 | 1
Gross Unrealized Losses | 19 | 58
Fair Value | 4,011 | 4,466
Corporate bonds and direct obligations of government agencies |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 70,069 | 76,839
Gross Unrealized Gains | 150 | 190
Gross Unrealized Losses | 239 | 270
Fair Value | 69,980 | 76,759
U.S. Treasury Obligations |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Amortized Cost | 23,037 | 19,273
Gross Unrealized Gains | 2 | 5
Gross Unrealized Losses | 6 | 13
Fair Value | $ 23,033 | $ 19,265

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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=73527792&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=73527792&loc=d3e27161-111563 + Details
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- Definition Amount before tax of unrealized loss 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 (c) -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563 + Details
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- Definition Amount of debt securities categorized neither as held-to-maturity nor trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26610-111562 Reference 3: 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=73527792&loc=d3e27161-111563 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 320 -Section 50 -Paragraph 2 -Subparagraph (b)-(g) -URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803 + Details
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