Schedule of Changes in Unrecognized Tax Benefits (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Income Tax Contingency [Line Items]
Unrecognized tax benefits at beginning of year	$ 129	$ 23	$ 44
Additions for tax positions related to current year		102	1
Additions for tax positions related to prior years	2	10	1
Reductions for tax positions related to prior years	(107)	(4)	(8)
Settlements with taxing authorities	(1)		(12)
Lapse of statute of limitations	(2)	(2)	(3)
Unrecognized tax benefits at end of year	21	129	23
Unrecognized tax benefits that, if recognized, would affect the effective income tax rate	$ 17	$ 115	$ 17

Unrecognized tax benefits increases resulting from prior period tax positions and settlements with tax authorities.

No definition available.

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The gross amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns as of the balance sheet date.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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The gross amount of decreases in unrecognized tax benefits resulting from tax positions taken in prior period tax returns, excluding amounts pertaining to examined tax returns.

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The gross amount of decreases in unrecognized tax benefits resulting from settlements with taxing authorities.

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The gross amount of increases in unrecognized tax benefits resulting from tax positions that have been or will be taken in the tax return for the current period, excluding amounts pertaining to examined tax returns.

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The gross amount of decreases in unrecognized tax benefits resulting from lapses of the applicable statutes of limitations.

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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