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Fair Value Measurements - Investment Impairments and Credit Loss Reserves (Details) - USD ($) $ in Thousands | 3 Months Ended |
--- | --- | ---
Apr. 26, 2020 | Jan. 27, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |
Increase in credit loss reserves on available-for-sale securities | $ 2,022 |
Increase in credit loss reserves on held-to-maturity securities | 400 |
Credit loss reserve for available-for-sale and held-to-maturity debt securities | 2,800 |
Impairment on non-marketable equity securities | $ 1,200 |
ASU 2016-13 | Cumulative Effect, Period Of Adoption, Adjustment |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |
Credit loss reserve on held-to-maturity securities |  | $ 400

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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=118942338&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=118955579&loc=SL82922897-210455 + Details
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