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Retirement-Related Benefits (Schedule of Contribution Expense Related to Defined Contribution Plans) (Details) - USD ($) $ in Millions | 12 Months Ended
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Jan. 31, 2018 | Jan. 31, 2017 | Jan. 31, 2016
Contribution expense from retirement plans [Line Items] |  |  |
Total contribution expense for defined contribution and benefit plans | $ 1,250 | $ 1,237 | $ 1,146
Domestic Plan [Member] |  |  |
Contribution expense from retirement plans [Line Items] |  |  |
Defined contribution plan, cost | 1,124 | 1,064 | 967
Foreign Plan [Member] |  |  |
Contribution expense from retirement plans [Line Items] |  |  |
Defined contribution plan, cost | $ 126 | $ 173 | $ 179

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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
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- Definition [Line Items] for Contribution expense from retirement plans [Table] + References No definition available. + Details
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- Definition Total Contribution Expense for Defined Contribution and Benefit Plans - The amount of the cost recognized during the period for defined contribution and defined benefit plans. + References No definition available. + Details
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- Details
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- Details
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