Basis of Presentation - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Feb. 28, 2014	Feb. 28, 2013	Feb. 28, 2014	Feb. 28, 2013	May 31, 2013
Summary Of Significant Accounting Policies [Line Items]
Advertising expenses	$ 233	$ 284	$ 665	$ 756
Shipping and handling cost	915	780	2,997	2,735
Assets, liabilities, revenues and expenses of foreign subsidiaries			less than 10% of our respective consolidated amounts
Demonstration equipment	$ 6,369		$ 6,369		$ 6,057
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