Convertible Senior Notes, Net - Schedule of Interest Expense (Details) - Senior Notes - USD ($) $ in Thousands	3 Months Ended
Apr. 30, 2020	Apr. 30, 2019
Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Contractual interest expense	$ 75	$ 216
Amortization of debt issuance costs	127	319
Amortization of debt discount	1,370	3,706
Total	1,572	$ 4,241
Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Contractual interest expense	331
Amortization of debt issuance costs	506
Amortization of debt discount	8,354
Total	$ 9,191

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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