Convertible Senior Notes - Schedule of Interest Expense for the Notes (Details) - Convertible Debt - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2021	Jul. 31, 2020	Jul. 31, 2021	Jul. 31, 2020
2024 Notes
Debt Instrument [Line Items]
Contractual interest expense	$ 67	$ 169	$ 199	$ 338
Amortization of debt discount	0	986	0	1,956
Amortization of issuance costs	44	68	644	133
Total	111	1,223	843	2,427
2026 Notes
Debt Instrument [Line Items]
Contractual interest expense	719	719	1,437	1,438
Amortization of debt discount	0	10,685	0	21,231
Amortization of issuance costs	838	455	1,675	897
Total	$ 1,557	$ 11,859	$ 3,112	$ 23,566