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Fair Value Measurements - Fair Value of Available-for-sale Securities (Details) - USD ($) $ in Thousands | May 02, 2020 | Aug. 03, 2019
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 229,944 | $ 196,124
Gross Unrealized Gains | 1,728 | 524
Gross Unrealized Losses | (9) | 0
Fair Value | 231,663 | 196,648
U.S. Treasury securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 69,644 | 49,807
Gross Unrealized Gains | 713 | 100
Gross Unrealized Losses | (5) | 0
Fair Value | 70,352 | 49,907
Commercial paper |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 31,154 | 29,761
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | 0
Fair Value | 31,154 | 29,761
Asset-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 46,513 | 42,587
Gross Unrealized Gains | 397 | 145
Gross Unrealized Losses | 0 | 0
Fair Value | 46,910 | 42,732
Corporate bonds |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 82,633 | 73,969
Gross Unrealized Gains | 618 | 279
Gross Unrealized Losses | (4) | 0
Fair Value | $ 83,247 | $ 74,248

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- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
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- Definition Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
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- Definition Amortized cost 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/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454 + Details
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