Acquisitions - Additional Information (Detail) (USD $)	3 Months Ended	6 Months Ended
	Nov. 30, 2014	Nov. 30, 2014
MEF
Business Acquisition [Line Items]
Business acquisition, date of acquisition agreement		Aug. 01, 2014
Total consideration for acquired entity		$ 38,392,000
Cash consideration for acquired entity		35,232,000
Working capital paid	3,399,000
Acquisition related costs	273,000	273,000
JRE
Business Acquisition [Line Items]
Business acquisition, date of acquisition agreement		Jul. 31, 2014
Cash consideration for acquired entity		1,571,000
DHybrid Systems Llc
Business Acquisition [Line Items]
Business acquisition, date of acquisition agreement		Oct. 20, 2014
Percentage of additional interest acquired by the company	79.59%	79.59%
Percentage of interest attributable to non-controlling interest	20.41%	20.41%
Total consideration for acquired entity		15,918,000
Contingent consideration estimated fair value	3,979,000	3,979,000
Contingent consideration to be paid upon achievement of net sales and gross margin thresholds	3,979,000	3,979,000
Cumulative net sales threshold beginning January 1, 2013	20,000,000	20,000,000
Gross margin threshold		50.00%
Cash consideration for acquired entity		$ 11,939,000