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Debt - Components of the Convertible Notes (Details) - USD ($)	3 Months Ended		9 Months Ended
	Oct. 24, 2020	Oct. 26, 2019	Oct. 24, 2020	Oct. 26, 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			6,732,000	$ 15,016,000
Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Debt instrument, face amount	57,681,000		57,681,000		$ 447,350,000
Less: Debt discount and debt issuance costs	(2,643,000)		(2,643,000)		(37,474,000)
Net carrying amount of Notes	55,038,000		55,038,000		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	(2,375,000)		(2,375,000)		(33,744,000)
Debt issuance cost	(268,000)		(268,000)		(3,730,000)
Net carrying amount of Notes	55,621,000		55,621,000		$ 422,526,000
Amortization of debt discount	$ 600,000	$ 5,100,000	$ 6,700,000	$ 15,000,000.0