Income Taxes - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2010
Income Taxes [Line Items]
Deferred tax assets related to net operating losses and tax credit carryforwards	$ 28,210	$ 25,606
Accrued interest and penalties related to unrecognized tax benefits	9,916	9,664
Unrecognized tax benefits, if recognized, would favorably affect our effective tax rate	32,064
Cumulative amount of earnings upon which U.S. income taxes have not been provided	335,522
Unrecognized tax position decrease due to settlements or expiration of the statute of limitations within the next twelve months, upper limit	10,000
Unrecognized tax position decrease due to settlements or expiration of the statute of limitations within the next twelve months, lower limit	0
Interest and penalties benefit (expense) related to income taxes	$ 677	$ (211)	$ 1,560