Segment Reporting and Related Disclosures - Revenues from Rental, Lease and Sale Group (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Aug. 31, 2014		Aug. 31, 2013
Revenue from External Customer [Line Items]
Rentals and leases	$ 33,889		$ 35,657
Sales of equipment and other revenues	27,982		24,511
Total revenues	61,871	[1]	60,168	[1]
T&M
Revenue from External Customer [Line Items]
Rentals and leases	29,249		30,820
Sales of equipment and other revenues	27,476		23,850
Total revenues	56,725		54,670
DP
Revenue from External Customer [Line Items]
Rentals and leases	4,640		4,837
Sales of equipment and other revenues	506		661
Total revenues	$ 5,146		$ 5,498

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