Industry Segments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jul. 31, 2014 Group Segment	Jul. 31, 2013 Home Depot Customer	Jul. 31, 2013 Total revenues Home Depot
Segment Reporting Information [Line Items]
Number of major business segments	3
Number of major product and service groups	4
Number of major customers		1
Percentage of total revenue			10.80%
Total revenue		$ 2.5