Taxes Schedule of Tax Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Reconciliation of Unrecognized Tax Benefits
Unrecognized tax benefits, beginning of year	$ 607	$ 838	$ 763
Increases related to prior year tax positions	388	164	7
Decreases related to prior year tax positions	(32)	(446)	(17)
Increases related to current year tax positions	145	119	174
Settlements during the period	(46)	(25)	(89)
Lapse in statutes of limitations	(12)	(43)	0
Unrecognized tax benefits, end of year	$ 1,100	$ 607	$ 838

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=SL6600010-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Unrecognized Tax Benefit
-URI http://asc.fasb.org/extlink&oid=6527854

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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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