Convertible Senior Notes - Schedule of Interest Expense for the Notes (Details) - Convertible Debt - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019
Debt Instrument [Line Items]
Contractual interest expense		$ 1,325
Amortization of debt discount		6,956
Amortization of issuance costs		415
Total		$ 8,696
2024 Notes
Debt Instrument [Line Items]
Contractual interest expense	$ 2,178
Amortization of debt discount	12,021
Amortization of issuance costs	767
Total	14,966
2026 Notes
Debt Instrument [Line Items]
Contractual interest expense	136
Amortization of debt discount	1,977
Amortization of issuance costs	82
Total	$ 2,195