Revenues from External Customers and Long-Lived Assets, by Geographical Areas (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
Revenues:
Total revenues	$ 57,876	[1]	$ 65,192	[1]	$ 118,044	[1]	$ 123,693	[1]
Net Long-Lived Assets:
Total net long-lived assets	245,404	[2]			245,404	[2]			248,682	[2]
U.S.
Revenues:
Total revenues	48,911	[1]	56,428	[1]	99,137	[1]	105,542	[1]
Net Long-Lived Assets:
Total net long-lived assets	201,365	[2]			201,365	[2]			198,956	[2]
Other
Revenues:
Total revenues	8,965	[1],[3]	8,764	[1],[3]	18,907	[1],[3]	18,151	[1],[3]
Net Long-Lived Assets:
Total net long-lived assets	$ 44,039	[2],[3]			$ 44,039	[2],[3]			$ 49,726	[2],[3]

[1] Revenues by country are based on the location of shipping destination, and not whether the order originates in the United States parent or a foreign subsidiary.

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

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