Face (par) amount of debt instrument at time of issuance.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
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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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- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Glossary Financing Activities
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Repayment of Long-Term Debt, Partial Extinguishment

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Repayments of Long-Term Debt, Matured

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Long-term Debt Schedule of Debt Maturities (Details) £ in Millions, $ in Millions	6 Months Ended
	Jul. 31, 2017 USD ($)	Jul. 31, 2016 USD ($)	Jan. 19, 2039 GBP (£)	Apr. 15, 2038 USD ($)	Aug. 15, 2037 USD ($)	Apr. 21, 2017 USD ($)	Apr. 05, 2017 USD ($)
Debt Instrument [Line Items]
Repayments of Long-term Debt	$ 4,177	$ 2,026
Unsecured debt
Debt Instrument [Line Items]
Repayments of Long-term Debt	3,375
Repayments of Long-Term Debt, Matured	1,500
Repayment of Long-Term Debt, Partial Extinguishment	1,875
Unsecured debt \| 5.375% Fixed Rate Debt, Due 2017 [Member]
Debt Instrument [Line Items]
Principal Amount							$ 1,000
Interest Rate							5.375%
Repayments of Long-term Debt	1,000
Unsecured debt \| 1.000% Fixed Rate Debt, Due 2017 [Member]
Debt Instrument [Line Items]
Principal Amount						$ 500
Interest Rate						1.00%
Repayments of Long-term Debt	500
Unsecured debt \| 6.500% Fixed Rate Debt, Due 2037 [Member]
Debt Instrument [Line Items]
Principal Amount					$ 3,000
Interest Rate					6.50%
Repayments of Long-term Debt	1,238
Unsecured debt \| 6.200% Fixed Rate Debt, Due 2038 [Member]
Debt Instrument [Line Items]
Principal Amount				$ 2,000
Interest Rate				6.20%
Repayments of Long-term Debt	178
Unsecured debt \| 4.875% Fixed Rate Debt, Due 2039 [Member]
Debt Instrument [Line Items]
Principal Amount \| £			£ 1,000
Interest Rate			4.875%
Repayments of Long-term Debt	$ 459