Debt and Financing Arrangements - Schedule of Interest Expense (Details) - Senior Notes - Convertible Senior Notes Due 2023 - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jul. 31, 2018	Jul. 31, 2018
Debt Instrument [Line Items]
Contractual interest expense	$ 216	$ 362
Amortization of debt issuance costs	288	478
Amortization of debt discount	3,554	5,935
Total	$ 4,058	$ 6,775

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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Amount of amortization expense attributable to debt issuance costs.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of the cost of borrowed funds accounted for as interest expense for debt.

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Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

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