Shareholder's Equity Shareholder's Equity (Schedule of Fair Value of Restricted Stock) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2013
Restricted stock and performance share units
Additional information related to restricted stock and performance share awards and restricted stock units
Fair value	$ 156	$ 116	$ 155
Unrecognized compensation cost	154	200	233
Weighted average remaining period to expense, years	1 year 3 months	2 years	2 years
Restricted stock units
Additional information related to restricted stock and performance share awards and restricted stock units
Fair value	218	189	168
Unrecognized compensation cost	$ 570	$ 497	$ 437
Weighted average remaining period to expense, years	1 year 8 months	2 years 1 month	1 year 8 months

Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

No definition available.

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- Definition

Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (e)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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- Definition

Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (d)(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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- Details

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