Taxes (Schedule of Tax Reconciliation) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2013
Reconciliation of Unrecognized Tax Benefits
Unrecognized tax benefits, beginning of year	$ 763us-gaap_UnrecognizedTaxBenefits	$ 818us-gaap_UnrecognizedTaxBenefits	$ 611us-gaap_UnrecognizedTaxBenefits
Increases related to prior year tax positions	7	41	88
Decreases related to prior year tax positions	(17)	(112)	(232)
Increases related to current year tax positions	174	133	431
Settlements during the period	(89)	(117)	(80)
Lapse in statutes of limitations	0	0	0
Unrecognized tax benefits, end of year	$ 838us-gaap_UnrecognizedTaxBenefits	$ 763us-gaap_UnrecognizedTaxBenefits	$ 818us-gaap_UnrecognizedTaxBenefits

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Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

+ References

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-Name Accounting Standards Codification

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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 increase 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 lapses of applicable statutes of limitations.

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