Income Taxes - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 31, 2012	Oct. 31, 2011	Oct. 31, 2012	Oct. 31, 2011	Jan. 31, 2012
Disclosure Income Taxes Additional Information [Abstract]
Effective Tax Rate	3.50%	(6.40%)	(1.10%)	(20.50%)
Period specific items benefit			$ (6,176)
Effective Income Tax Rate Forecast			3.00%
U.S. federal statutory rate			35.00%
Income taxes associated with uncertain income tax positions	27,706		27,706
Liability for Uncertain Tax Positions, Current	5,535		5,535
Income tax liability	$ 22,171		$ 22,171		$ 34,257