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Shareholders' Equity (Schedule of Fair Value of Restricted Stock) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Jan. 31, 2018 | Jan. 31, 2017 | Jan. 31, 2016
Restricted stock and performance share units |  |  |
Additional information related to restricted stock and performance share awards and restricted stock units |  |  |
Fair value | $ 181 | $ 149 | $ 142
Unrecognized compensation cost | $ 291 | $ 211 | $ 133
Weighted average remaining period to expense, years | 1 year 2 months | 1 year 3 months | 1 year 3 months
Restricted stock units |  |  |
Additional information related to restricted stock and performance share awards and restricted stock units |  |  |
Fair value | $ 344 | $ 261 | $ 237
Unrecognized compensation cost | $ 972 | $ 986 | $ 628
Weighted average remaining period to expense, years | 1 year 9 months | 1 year 11 months | 1 year 8 months

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- Definition Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition 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. + References No definition available. + Details
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