Segment Reporting and Related Disclosures - Revenues from Rental, Lease and Sale Group (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Nov. 30, 2015	Nov. 30, 2014	Nov. 30, 2015	Nov. 30, 2014
Revenue from External Customer [Line Items]
Rentals and leases		$ 32,173	$ 33,469	$ 64,476	$ 67,358
Sales of equipment and other revenues		11,137	26,234	32,177	54,216
Total revenues	[1]	43,310	59,703	96,653	121,574
Depreciation		14,340	14,670	28,941	28,585
T&M | Operating Segments
Revenue from External Customer [Line Items]
Rentals and leases		27,467	28,789	54,597	58,038
Sales of equipment and other revenues		10,489	25,758	31,032	53,233
Total revenues		37,956	54,547	85,629	111,271
Depreciation		13,246	13,603	26,695	26,529
DP | Operating Segments
Revenue from External Customer [Line Items]
Rentals and leases		4,706	4,680	9,879	9,320
Sales of equipment and other revenues		648	476	1,145	983
Total revenues		5,354	5,156	11,024	10,303
Depreciation		$ 1,094	$ 1,067	$ 2,246	$ 2,056

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