Convertible Senior Notes - Schedule of Interest Expense for the Notes (Details) - Convertible Debt - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2021	Oct. 31, 2020	Oct. 31, 2021	Oct. 31, 2020
2024 Notes
Debt Instrument [Line Items]
Contractual interest expense	$ 4	$ 168	$ 203	$ 506
Amortization of debt discount	0	1,002	0	2,958
Amortization of issuance costs	2	70	646	203
Total	6	1,240	849	3,667
2026 Notes
Debt Instrument [Line Items]
Contractual interest expense	719	718	2,156	2,156
Amortization of debt discount	0	10,826	0	32,058
Amortization of issuance costs	840	469	2,515	1,366
Total	$ 1,559	$ 12,013	$ 4,671	$ 35,580