Organization and Basis of Presentation - Recently Adopted Accounting Guidance (Details) - USD ($) $ in Thousands	Apr. 26, 2020	Jan. 27, 2020	Jan. 26, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	$ (620,928)		$ (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