Segment Reporting and Related Disclosures - Revenues from Rental, Lease and Sale Group (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Nov. 30, 2014		Nov. 30, 2013		Nov. 30, 2014		Nov. 30, 2013
Revenue from External Customer [Line Items]
Rentals and leases	$ 33,469		$ 35,205		$ 67,358		$ 70,862
Sales of equipment and other revenues	26,234		22,671		54,216		47,182
Total revenues	59,703	[1]	57,876	[1]	121,574	[1]	118,044	[1]
T&M
Revenue from External Customer [Line Items]
Rentals and leases	28,789		31,060		58,038		61,880
Sales of equipment and other revenues	25,758		22,263		53,233		46,113
Total revenues	54,547		53,323		111,271		107,993
DP
Revenue from External Customer [Line Items]
Rentals and leases	4,680		4,145		9,320		8,982
Sales of equipment and other revenues	476		408		983		1,069
Total revenues	$ 5,156		$ 4,553		$ 10,303		$ 10,051

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