Net Loss Per Share - Narrative (Details) - USD ($)	3 Months Ended
Apr. 30, 2020	Apr. 30, 2019
Debt Instrument [Line Items]
Dilutive effect on securities	$ 0	$ 0
Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Value of shares issuable under warrants granted (in dollars per share)	$ 68.06
Convertible Senior Notes Due 2023 \| Senior Notes
Debt Instrument [Line Items]
Conversion price (in dollars per share)	48.36
Convertible Senior Notes Due 2025 \| Senior Notes
Debt Instrument [Line Items]
Conversion price (in dollars per share)	$ 188.71

Exercise price per share or per unit of warrants or rights outstanding.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(i)(4))
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The price per share of the conversion feature embedded in the debt instrument.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
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+ References

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Amount of increase (decrease) to net income used for calculating diluted earnings per share (EPS), resulting from the assumed exercise stock options, restrictive stock units (RSUs), convertible preferred stock of an employee stock ownership plan (ESOP), and other dilutive convertible securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
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