Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Aug. 31, 2015	Aug. 31, 2014
Summary Of Significant Accounting Policies [Line Items]
Rental and lease equipment impairment	$ 443	$ 0
Advertising expenses	217	169
Shipping and handling cost	$ 944	1,036
Assets, liabilities, revenues and expenses of foreign subsidiaries	0.1
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	$ 443	$ 0