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Debt - Components of the Convertible Notes (Details) - USD ($)	3 Months Ended
	Apr. 25, 2020	Apr. 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
Amortization of debt discount	4,341,000	$ 4,932,000
Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Debt instrument, face amount	266,627,000		$ 447,350,000
Less: Debt discount and debt issuance costs	(20,390,000)		(37,474,000)
Net carrying amount of Notes	246,237,000		409,876,000
0.75% Convertible Senior Notes Due 2021
Debt Instrument [Line Items]
Debt instrument, face amount	292,997,000		460,000,000	$ 485,000,000.0
Debt Instrument, Unamortized Discount	(18,349,000)		(33,744,000)
Debt issuance cost	(2,041,000)		(3,730,000)
Net carrying amount of Notes	272,607,000		$ 422,526,000
Amortization of debt discount	$ 4,300,000	$ 4,900,000