Basis of Presentation - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2013	Nov. 30, 2012	Nov. 30, 2013	Nov. 30, 2012	May 31, 2013
Summary Of Significant Accounting Policies [Line Items]
Advertising expenses	$ 207	$ 239	$ 432	$ 472
Shipping and handling cost	1,153	984	2,082	1,955
Assets, liabilities, revenues and expenses of foreign subsidiaries			Less than 10% of consolidated amounts
Demonstration equipment	$ 5,781		$ 5,781		$ 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