Convertible Senior Notes - Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Feb. 02, 2020	Jan. 31, 2019	Jan. 31, 2018
Debt Instrument [Line Items]
Total amortization of debt discount and debt issuance costs	$ 27,179	$ 21,031	$ 0
Convertible Senior Notes
Debt Instrument [Line Items]
Amortization of debt discount	25,344	19,611
Amortization of debt issuance costs	1,835	1,420
Total amortization of debt discount and debt issuance costs	27,179	21,031
Contractual interest expense	718	584
Total interest expense related to the Notes	$ 27,897	$ 21,615
Effective interest rate of the liability component ( as a percent)	5.60%	5.60%