Segment Reporting - Additional Information (Detail)	12 Months Ended
	Jan. 31, 2012 Person	Jan. 31, 2011 Person	Jan. 31, 2010 Person
Number of customer accounted for approximately 10% or more of total revenues	0	0	0
Description of external customer accounted for total revenues	No single customer accounted for 10% or more of total revenues.	No single customer accounted for 10% or more of total revenues.	No single customer accounted for 10% or more of total revenues.