Financial Instruments - Additional Information (Details) - USD ($)	3 Months Ended
Apr. 30, 2021	Apr. 30, 2020	Jan. 31, 2021
Investments, All Other Investments [Abstract]
Securities in a continuous unrealized loss position for more than 12 months	$ 0		$ 0
Allowance for credit loss	0	$ 0
Securities, writeoff	0	0
Gain (loss) from sale or redemption of available for sale securities	0	0
Sales and maturities of marketable securities	4,000,000.0	$ 0
Direct investments in privately held companies	129,800,000		$ 134,100,000
Equity method investment, realized gain (loss) on disposal	$ 8,100,000

Amount of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922900-210455

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
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-Section 50
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 2
-Subparagraph (aaa)
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Section 45
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- Definition

Amount of writeoff of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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- Definition

Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27337-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), investment in debt security measured at amortized cost (held-to-maturity) and investment in debt security measured at fair value with change in fair value recognized in net income (trading).

+ References

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- Definition

Amount of gain (loss) on sale or disposal of an equity method investment.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Amount of investment in equity security without readily determinable fair value.

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The cash inflow associated with the aggregate amount received by the entity through sale or maturity of marketable securities (held-to-maturity or available-for-sale) during the period.

+ References

No definition available.

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