Convertible Senior Notes - Schedule of Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2020	Jul. 31, 2019
Debt Instrument
Amortization of debt issuance costs			$ (44,738)	$ (39,095)
Convertible Senior Notes \| 2023 Notes
Debt Instrument
Coupon interest expense	$ 1,174	$ 1,581	2,755	3,162
Amortization of debt discount (conversion option)	9,604	12,218	22,022	23,813
Amortization of debt issuance costs	375	477	860	930
Total interest expense	11,153	14,276	25,637	27,905
Convertible Senior Notes \| 2025 Notes
Debt Instrument
Coupon interest expense	2,426	2,426	4,852	4,852
Amortization of debt discount (conversion option)	7,649	7,197	14,961	13,968
Amortization of debt issuance costs	210	198	411	384
Total interest expense	10,285	$ 9,821	$ 20,224	$ 19,204
Convertible Senior Notes \| 2027 Notes
Debt Instrument
Coupon interest expense	2,174
Amortization of debt discount (conversion option)	6,230
Amortization of debt issuance costs	254
Total interest expense	$ 8,658

Convertible Debt, Coupon Interest Expense

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- Definition

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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Amount of amortization expense attributable to debt discount (premium) and debt issuance costs.

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- Definition

The after-tax amount of interest recognized in the period associated with any convertible debt.

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