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Debt - Components of the Convertible Notes (Details) - USD ($)	3 Months Ended		9 Months Ended
	Oct. 26, 2019	Oct. 27, 2018	Oct. 26, 2019	Oct. 27, 2018	Jan. 26, 2019	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			15,016,000	$ 14,223,000
Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Debt instrument, face amount	463,757,000		463,757,000		$ 467,104,000
Less: Debt discount and debt issuance costs	(45,257,000)		(45,257,000)		(61,801,000)
Net carrying amount of Notes	418,500,000		418,500,000		405,303,000
0.75% Convertible Senior Notes Due 2021
Debt Instrument [Line Items]
Debt instrument, face amount	485,000,000		485,000,000		485,000,000	$ 485,000,000.0
Debt Instrument, Unamortized Discount	(40,780,000)		(40,780,000)		(55,795,000)
Debt issuance cost	(4,477,000)		(4,477,000)		(6,006,000)
Net carrying amount of Notes	439,743,000		439,743,000		$ 423,199,000
Amortization of debt discount	$ 5,100,000	$ 4,800,000	$ 15,000,000.0	$ 14,200,000