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Contingencies (Schedule of Foreign Corrupt Practices Act Expenses) (Details) - USD ($) $ in Millions | 12 Months Ended
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Jan. 31, 2018 | Jan. 31, 2017 | Jan. 31, 2016
Foreign Corrupt Practices Act Expenses [Line Items] |  |  |
Foreign corrupt practices act related expenses | $ 99 | $ 40 | $ 126
Compliance programs and organizational enhancements |  |  |
Foreign Corrupt Practices Act Expenses [Line Items] |  |  |
Foreign corrupt practices act related expenses | 19 | 14 | 31
Inquiry and investigation expense |  |  |
Foreign Corrupt Practices Act Expenses [Line Items] |  |  |
Foreign corrupt practices act related expenses | $ 80 | $ 26 | $ 95

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