Fair Value Measurements - Investment Impairments and Credit Loss Reserves (Details) - USD ($)	3 Months Ended		9 Months Ended
	Oct. 31, 2021	Oct. 25, 2020	Oct. 31, 2021	Oct. 25, 2020	Jan. 31, 2021	Jan. 26, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Credit loss reserve for held-to-maturity debt securities and available for sale debt securities	$ 4,300,000		$ 4,300,000		$ 3,400,000
Increase in credit loss reserve for available-for-sale and held-to-maturity debt securities	$ 200,000	$ 300,000	$ 900,000	$ 2,700,000
Impairment on non-marketable equity securities		$ 0		$ 2,900,000
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						$ 400,000