Segment Reporting - Additional Information (Detail)	12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Concentration Risk [Line Items]
Number of customer accounted for approximately 10% or more of total revenues	0
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
Customer Concentration Risk [Member] | Sales Revenue, Goods and Services, Net [Member]
Concentration Risk [Line Items]
Customer percent of total revenues	10.00%