Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets.

Reference 1: 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

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Section 50
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-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 210
-SubTopic 20
-Section 55
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226016-175313

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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
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-Topic 210
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-Section 50
-Paragraph 3
-Subparagraph (d)(2)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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-Section 50
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-Subparagraph (b)
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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