Revenues from Rental, Lease and Sale Segment (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	May. 31, 2015	Feb. 28, 2015	Nov. 30, 2014	Aug. 31, 2014	May. 31, 2014	Feb. 28, 2014	Nov. 30, 2013	Aug. 31, 2013	May. 31, 2015	May. 31, 2014	May. 31, 2013
Revenue from External Customer [Line Items]
Rentals and leases									$ 129,255	$ 137,417	$ 136,591
Sales of equipment and other revenues									109,074	103,720	112,140
Total revenues	$ 60,413	$ 56,342	$ 59,703	$ 61,871	$ 61,077	$ 62,016	$ 57,876	$ 60,168	238,329	241,137	248,731
T&M equipment
Revenue from External Customer [Line Items]
Rentals and leases									111,327	120,629	120,846
Sales of equipment and other revenues									107,270	101,898	109,700
Total revenues									218,597	222,527	230,546
DP equipment
Revenue from External Customer [Line Items]
Rentals and leases									17,928	16,788	15,745
Sales of equipment and other revenues									1,804	1,822	2,440
Total revenues									$ 19,732	$ 18,610	$ 18,185