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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226016-175313

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=d3e41678-113959

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-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

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- Definition

Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities.

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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.

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Nominal or face amount used to calculate payments on a nonderivative instrument.

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- Definition

Threshold Of Derivative Liability Position Requiring Cash Collateral

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Derivatives (Details) $ in Millions, ¥ in Billions, £ in Billions	12 Months Ended
	Jan. 31, 2019 JPY (¥)	Jan. 31, 2019 GBP (£)	Jan. 31, 2018 JPY (¥)	Jan. 31, 2018 GBP (£)	Jan. 31, 2019 USD ($)	Jan. 31, 2018 USD ($)
Derivative [Line Items]
Cash collateral held from counterparties					$ 220	$ 279
Threshold of derivative liability position requiring cash collateral					150
Cash collateral posted with counterparties					$ 0	$ 0
Designated as hedging instrument \| Net investment hedging \| Japan
Derivative [Line Items]
Notional amount of nonderivative instruments \| ¥	¥ 180.0		¥ 180.0
Designated as hedging instrument \| Net investment hedging \| United Kingdom
Derivative [Line Items]
Notional amount of nonderivative instruments \| £		£ 1.7		£ 1.7