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Note 4 - Fair Value Measurements (Details Textual) - USD ($) $ / shares in Units, $ in Millions | 12 Months Ended
--- | ---
Jan. 31, 2020 | Jan. 31, 2019 | Jan. 31, 2018
Derivative Instrument, Shares of Common Stock Held | 251,422 |  |
Derivative Instrument, Common Shares Held, Per Share | $ 22.37 |  |
General and Administrative Expense [Member] |  |  |
Derivative, Gain on Derivative | $ 4.0 | $ 1.2 | $ 1.1

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- Definition The per share amount of common shares held by certain derivative instruments entered into by the company. + References No definition available. + Details
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Namespace Prefix: | dsgx_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

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- Definition The number of shares held by certain derivative instruments entered into by the company. + References No definition available. + Details
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Namespace Prefix: | dsgx_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

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- Definition Amount of increase in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959 + Details
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Period Type: | duration

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |