Share Repurchases (Schedule Of Company's Share Repurchases) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
Apr. 30, 2018	Apr. 30, 2017
Equity, Class of Treasury Stock [Line Items]
Total number of shares repurchased	5.5	31.1
Average price paid per share	$ 97.75	$ 70.25
Total amount paid for share repurchases	$ 539	$ 2,185

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.

No definition available.

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Total cost of shares repurchased divided by the total number of shares repurchased.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 45
-Paragraph 1
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Number of shares that have been repurchased during the period and are being held in treasury.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
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Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21463-112644

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