Segment Reporting and Related Disclosures - Revenues from External Customers and Long-Lived Assets, by Geographical Areas (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Aug. 31, 2014		Aug. 31, 2013		May 31, 2014
Revenues:
Total revenues	$ 61,871	[1]	$ 60,168	[1]
Net Long-Lived Assets:
Total net long-lived assets	235,042	[2]			235,010	[2]
U.S.
Revenues:
Total revenues	51,152	[1]	50,225	[1]
Net Long-Lived Assets:
Total net long-lived assets	190,828	[2]			188,343	[2]
Other
Revenues:
Total revenues	10,719	[1],[3]	9,943	[1],[3]
Net Long-Lived Assets:
Total net long-lived assets	$ 44,214	[2],[3]			$ 46,667	[2],[3]

[1] Revenues by country are based on the shipping destination.

[2] Net long-lived assets include rental and lease equipment and other property, net of accumulated depreciation and amortization.

[3] Other consists of countries other than the U.S. Each foreign country individually accounts for less than 10% of the total revenues and long-lived assets.