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Fair Value Measurements - Narrative (Details) - USD ($) | 12 Months Ended |
--- | --- | ---
Jan. 31, 2021 | Jan. 26, 2020 | Jan. 27, 2019 | Jan. 27, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Transfers of financial assets or liabilities between levels |  | $ 0 |  |
Debt Securities, Available-for-sale, Change in Present Value, Expense (Reversal) | $ 313,000 |  |  |
Debt Securities, Available For Sale And Held To Maturity, Allowance For Credit Loss | 3,400,000 |  |  |
Non-Marketable Equity Securities Impairment | 3,900,000 |  |  |
Investment impairments and credit loss reserves | 6,769,000 | 1,211,000 | $ 30,000,000 |
Equity securities, loss |  | 500,000 |  |
Debt Securities, Loss |  | 700,000 |  |
Increase in credit loss reserve | $ 2,927,000 |  |  |
Cumulative Effect, Period of Adoption, Adjustment | Accounting Standards Update 2016-13 |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss |  | $ 400,000 |  | $ 400,000

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- Definition Amount of increase (decrease) in allowance for credit loss 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/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922900-210455 + Details
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- Definition Amount of expense (reversal of expense) for expected credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), from change in present value of expected cash flows. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82922868-210454 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922897-210455 + Details
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