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Debt - Components of the Convertible Notes (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jul. 25, 2020	Jul. 27, 2019	Jul. 25, 2020	Jul. 27, 2019	Jan. 25, 2020	Sep. 15, 2015
Debt Instrument [Line Items]
Equity component of 0.75% senior convertible notes due 2021, net	$ 112,600,000		$ 112,600,000
Amortization of debt discount			6,089,000	$ 9,947,000
Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Debt instrument, face amount	56,662,000		56,662,000		$ 447,350,000
Less: Debt discount and debt issuance costs	(3,356,000)		(3,356,000)		(37,474,000)
Net carrying amount of Notes	53,306,000		53,306,000		409,876,000
0.75% Convertible Senior Notes Due 2021
Debt Instrument [Line Items]
Debt instrument, face amount	58,264,000		58,264,000		460,000,000	$ 485,000,000.0
Debt Instrument, Unamortized Discount	(3,018,000)		(3,018,000)		(33,744,000)
Debt issuance cost	(338,000)		(338,000)		(3,730,000)
Net carrying amount of Notes	54,908,000		54,908,000		$ 422,526,000
Amortization of debt discount	$ 1,700,000	$ 5,000,000.0	$ 6,100,000	$ 9,900,000