Financial Instruments - Non-Marketable Equity Securities (Details) - USD ($) $ in Millions	12 Months Ended
Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2019
Equity Securities without Readily Determinable Fair Value, Annual Amount [Abstract]
Upward adjustments	$ 6.6	$ 3.2	$ 6.2
Negative adjustments, including impairments	(51.6)	(4.2)	(4.8)
Net adjustments	(45.0)	$ (1.0)	$ 1.4
Equity Securities without Readily Determinable Fair Value, Impairment Loss, Cumulative Amount [Abstract]
Upward adjustments	16.0
Negative adjustments, including impairments	(60.6)
Net adjustments	$ (44.6)

No definition available.

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- Definition

Amount of loss from downward price adjustment on investment in equity security without readily determinable fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117539-209714

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- Definition

Amount of cumulative loss from downward price adjustment on investment in equity security without readily determinable fair value.

+ References

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- Definition

Amount of impairment loss on investment in equity security without readily determinable fair value.

+ References

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Amount of cumulative impairment loss on investment in equity security without readily determinable fair value.

+ References

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- Definition

Amount of gain from upward price adjustment on investment in equity security without readily determinable fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117539-209714

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- Definition

Amount of cumulative gain from upward price adjustment on investment in equity security without readily determinable fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117539-209714

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