Schedule of Changes in Unrecognized Tax Benefits (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012
Income Tax Contingency [Line Items]
Unrecognized tax benefits at beginning of year	$ 21	$ 129	$ 23
Additions for tax positions related to current year	0	0	102
Additions for tax positions related to prior years	2	2	10
Reductions for tax positions related to prior years	0	(107)	(4)
Decrease in unrecognized tax benefits due to resolutions with tax authorities	0	1	0
Lapse of statute of limitations	(9)	(2)	(2)
Unrecognized tax benefits at end of year	14	21	129
Unrecognized tax benefits that, if recognized, would affect the effective income tax rate	$ 6	$ 10	$ 108