Segment Reporting - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Jan. 31, 2013
Entity Wide Portfolio Carrying Amount, Major Customer [Line Items]
Percentage of revenue	82.00%
Accounts receivable from major customers	21.7		17.6
Customer A [Member]
Entity Wide Portfolio Carrying Amount, Major Customer [Line Items]
Threshold limit	10.00%	10.00%	10.00%
Percentage of revenue		75.00%
Customer B [Member]
Entity Wide Portfolio Carrying Amount, Major Customer [Line Items]
Threshold limit	10.00%		10.00%