Segment Reporting and Related Disclosures - Revenues from External Customers and Long-Lived Assets, by Geographical Areas (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Nov. 30, 2015	Nov. 30, 2014	Nov. 30, 2015	Nov. 30, 2014	May. 31, 2015
Revenues:
Total revenues	[1]	$ 43,310	$ 59,703	$ 96,653	$ 121,574
Net Long-Lived Assets:
Total net long-lived assets	[2]	230,080		230,080		$ 244,791
U.S.
Revenues:
Total revenues	[1]	35,576	50,245	79,923	101,397
Net Long-Lived Assets:
Total net long-lived assets	[2]	180,978		180,978		197,514
Other
Revenues:
Total revenues	[1],[3]	7,734	$ 9,458	16,730	$ 20,177
Net Long-Lived Assets:
Total net long-lived assets	[2],[3]	$ 49,102		$ 49,102		$ 47,277

[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 consolidated revenues and net long-lived assets.