Segment Reporting and Related Disclosures - Revenues from Rental, Lease and Sale Group (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Feb. 28, 2015		Feb. 28, 2014		Feb. 28, 2015		Feb. 28, 2014
Revenue from External Customer [Line Items]
Rentals and leases	$ 30,252		$ 32,485		$ 97,610		$ 103,347
Sales of equipment and other revenues	26,090		29,531		80,306		76,713
Total revenues	56,342	[1]	62,016	[1]	177,916	[1]	180,060	[1]
T&M
Revenue from External Customer [Line Items]
Rentals and leases	26,372		28,793		84,410		90,673
Sales of equipment and other revenues	25,799		29,221		79,033		75,334
Total revenues	52,171		58,014		163,443		166,007
DP
Revenue from External Customer [Line Items]
Rentals and leases	3,880		3,692		13,200		12,674
Sales of equipment and other revenues	291		310		1,273		1,379
Total revenues	$ 4,171		$ 4,002		$ 14,473		$ 14,053

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