Revenues from Rental, Lease and Sale Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	May 31, 2013	Feb. 28, 2013	Nov. 30, 2012	Aug. 31, 2012	May 31, 2012	Feb. 29, 2012	Nov. 30, 2011	Aug. 31, 2011	May 31, 2013		May 31, 2012		May 31, 2011
Revenue from External Customer [Line Items]
Rentals and leases									$ 136,591		$ 129,737		$ 118,062
Sales of equipment and other revenues									112,140		118,817		110,667
Total revenues	60,366	64,672	65,192	58,501	68,182	60,079	61,643	58,650	248,731	[1]	248,554	[1]	228,729	[1]
T&M equipment
Revenue from External Customer [Line Items]
Rentals and leases									120,846		113,540		101,273
Sales of equipment and other revenues									109,700		116,417		108,450
Total revenues									230,546		229,957		209,723
DP equipment
Revenue from External Customer [Line Items]
Rentals and leases									15,745		16,197		16,789
Sales of equipment and other revenues									2,440		2,400		2,217
Total revenues									$ 18,185		$ 18,597		$ 19,006

[1] Revenues by country are based on the location of shipping destination, whether the order originates in the U.S. parent or a foreign subsidiary.