Convertible Senior Notes, Net - Schedule of Interest Expense (Details) - Senior Notes - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Contractual interest expense	$ 27	$ 99	$ 154	$ 530
Amortization of debt issuance costs	49	214	266	862
Amortization of debt discount	511	2,403	2,839	9,868
Total	587	2,716	3,259	11,260
Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Contractual interest expense	332	188	994	188
Amortization of debt issuance costs	530	275	1,554	275
Amortization of debt discount	8,526	4,649	25,320	4,649
Total	9,388	$ 5,112	27,868	$ 5,112
Convertible Senior Notes Due 2026
Debt Instrument [Line Items]
Contractual interest expense	1,078		1,653
Amortization of debt issuance costs	318		483
Amortization of debt discount	10,997		16,799
Total	$ 12,393		$ 18,935

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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