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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