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Cash and Investments - Narrative (Details) | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 29, 2018 USD ($) investment | Jun. 30, 2017 USD ($) | Jun. 29, 2018 USD ($) investment | Jun. 30, 2017 USD ($) | Dec. 29, 2017 investment
Investments, Debt and Equity Securities [Abstract] |  |  |  |  |
Gain (loss) on sales of investments available-for-sale | $ 0 | $ 0 | $ 0 | $ 0 |
Number of investments in an unrealized loss position | investment | 149 |  | 149 |  | 134
Other-than-temporary impairment charges on available-for-sale securities | $ 0 | $ 0 | $ 0 | $ 0 |

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- Definition Number of investment positions in available-for-sale investments in a continuous unrealized loss position for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563 + Details
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- Definition The amount by which the fair value of an investment in debt and equity securities categorized as Available-for-sale is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 8A -URI http://asc.fasb.org/extlink&oid=82896770&loc=SL6284422-111562 + Details
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