Segment Reporting and Related Disclosures (Details Textual) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Aug. 31, 2012 Customer Segment	Aug. 31, 2011 Customer	May 31, 2012
Segment Reporting and Related Disclosures (Additional Textual) [Abstract]
Number of Operating segment	2
Minimum percentage of revenue accounted for major customer	10.00%
Number of major customer accounted	0	0
Goodwill and other intangible assets	$ 4,269		$ 4,310
T&M [Member]
Segment Reporting and Related Disclosures (Textual) [Abstract]
Equipment pool, based on acquisition cost	415,955		409,686
DP [Member]
Segment Reporting and Related Disclosures (Textual) [Abstract]
Equipment pool, based on acquisition cost	$ 37,300		$ 37,595