Convertible Senior Notes - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended
May 03, 2020	Apr. 30, 2019
Debt Instrument [Line Items]
Total amortization of debt discount and debt issuance costs	$ 6,936	$ 6,490
Convertible Senior Notes
Debt Instrument [Line Items]
Amortization of debt discount	6,468	6,052
Amortization of debt issuance costs	468	438
Total amortization of debt discount and debt issuance costs	6,936	6,490
Contractual interest expense	177	177
Total interest expense related to the Notes	$ 7,113	$ 6,667
Effective interest rate of the liability component	5.60%	5.60%

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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