Organization and Basis of Presentation - Recently Adopted Accounting Guidance (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Apr. 26, 2020	Jul. 26, 2020	Jan. 27, 2020	Jan. 26, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounting Standards Update	us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201613Member
Retained earnings		$ (637,053)		$ (611,607)
ASU 2016-13 | Cumulative Effect, Period Of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings			$ 300
Credit loss reserve on held-to-maturity securities			$ 400