Industry Segments - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Jan. 31, 2015 Customer	Jan. 31, 2014 Customer	Jan. 31, 2015 Customer Segment Group	Jan. 31, 2014 Customer
Segment Reporting Information [Line Items]
Number of major business segments			3
Number of major product and service groups			4
Number of major customers	0	0	0	0
Customer Concentration Risk | Total revenues | Minimum
Segment Reporting Information [Line Items]
Percentage of total revenue	10.00%	10.00%	10.00%	10.00%