Segment Reporting - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Oct. 31, 2012	Oct. 31, 2011	Oct. 31, 2012	Oct. 31, 2011
Concentration Risk [Line Items]
Number of customer accounted for approximately 10% or more of total revenues	0		0	1
Description of external customer accounted for total revenues	no single customer accounted for 10% or more of our total revenues	no single customer accounted for 10% or more of our total revenues	no single customer accounted for 10% or more of our total revenues	one customer accounted for 13% of our total revenues
Customer Concentration Risk [Member] | Sales Revenue, Goods and Services, Net [Member]
Concentration Risk [Line Items]
Customer percent of total revenues	10.00%		10.00%	13.00%