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Derivative Financial Instruments (Details) $ in Millions, ¥ in Billions, £ in Billions | 12 Months Ended |  |
--- | --- | --- | ---
Jan. 31, 2018 JPY (¥) | Jan. 31, 2018 GBP (£) | Jan. 31, 2017 JPY (¥) | Jan. 31, 2017 GBP (£) | Jan. 31, 2018 USD ($) | Jan. 31, 2017 USD ($)
Derivative [Line Items] |  |  |  |  |  |
Cash collateral held from counterparties |  |  |  |  | $ 279 | $ 242
Threshold of derivative liability position requiring cash collateral |  |  |  |  | 150 |
Cash collateral posted with counterparties |  |  |  |  | $ 0 | $ 0
Designated as hedging instrument | Net investment hedging | United Kingdom |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Notional amount of nonderivative instruments | £ |  | £ 1.7 |  | £ 2.5 |  |
Designated as hedging instrument | Net investment hedging | Japan |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Notional amount of nonderivative instruments | ¥ | ¥ 180.0 |  | ¥ 10.0 |  |  |

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- Definition Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226016-175313 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84234895&loc=d3e41678-113959 + 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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- Definition Nominal or face amount used to calculate payments on a nonderivative instrument. + References No definition available. + Details
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