Financial Instruments (Non-Marketable Equity Securities) (Details) - USD ($) $ in Millions	6 Months Ended
Jul. 31, 2020	Jul. 31, 2019
Equity Securities without Readily Determinable Fair Value, Annual Amount [Abstract]
Upward adjustments	$ 3.0	$ 1.7
Negative adjustments, including impairments	(34.8)	(3.4)
Net adjustments	(31.8)	$ (1.7)
Equity Securities without Readily Determinable Fair Value, Impairment Loss, Cumulative Amount [Abstract]
Upward adjustments	12.4
Negative adjustments, including impairments	(43.8)
Net adjustments	$ (31.4)

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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.

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- 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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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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