Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Nov. 30, 2015	Nov. 30, 2014	Nov. 30, 2015	Nov. 30, 2014
Summary Of Significant Accounting Policies [Line Items]
Rental and lease equipment impairment			$ 443	$ 0
Advertising expenses	$ 373	$ 250	590	419
Shipping and handling cost	929	$ 1,085	$ 1,873	2,121
Assets, liabilities, revenues and expenses of foreign subsidiaries			0.1
Restatement of Prior Year Income, Gross				$ 1,300
Minimum
Summary Of Significant Accounting Policies [Line Items]
Operating lease agreements Period			1 year
Finance lease agreements Period			1 year
Maximum
Summary Of Significant Accounting Policies [Line Items]
Operating lease agreements Period			3 years
Finance lease agreements Period			3 years
Period for demonstration equipment included in other assets			2 years
T&M
Summary Of Significant Accounting Policies [Line Items]
Rental and lease equipment impairment	$ 0		$ 443