Effective Tax Rate and Period Specific Income Tax Expense (Benefit) (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
Effective Tax Rate and Period specific Income Tax Expense (Benefit)
Effective Tax Rate	3.50%	(6.40%)	(1.10%)	(20.50%)
Period specific items benefit			$ (6,176)