Acquisitions - Additional Information (Detail) (USD $)				0 Months Ended	12 Months Ended	0 Months Ended
	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012	Aug. 14, 2013 Taylor Manufacturing Systems, USA, LLC	Apr. 30, 2014 Taylor Manufacturing Systems, USA, LLC	Aug. 14, 2013 Taylor Manufacturing Systems, USA, LLC Current Technology
Business Acquisition [Line Items]
Business acquisition, purchase price				$ 1,807,000
Business acquisition, purchase price paid in cash				1,191,000
Business acquisition, working capital adjustments				50,000
Business acquisition, additional cash payments payable in each of three years following closing				200,000
Business acquisition, additional cash payments payable in first anniversary				200,000
Business acquisition, additional cash payments payable in second and third anniversaries				366,000
Business acquisition costs incurred					68,500
Business acquisition, purchase price allocate to goodwill	$ 13,819,000	$ 12,601,000	$ 12,601,000	$ 1,218,000
Remaining estimated economic life of the product						4 years