Basis of Presentation - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Aug. 31, 2014	Aug. 31, 2013	May 31, 2014
Summary Of Significant Accounting Policies [Line Items]
Advertising expenses	$ 169	$ 225
Shipping and handling cost	1,036	930
Assets, liabilities, revenues and expenses of foreign subsidiaries	10.00%
Demonstration equipment	$ 9,396		$ 6,659
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