Segment Reporting and Related Disclosures (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Aug. 31, 2012	Aug. 31, 2011
Revenues from rental, lease and sale segment
Rentals and leases	$ 33,665	$ 31,309
Sales of equipment and other revenues	24,836	27,341
Total revenues	58,501	58,650
T&M [Member]
Revenues from rental, lease and sale segment
Rentals and leases	29,605	26,602
Sales of equipment and other revenues	24,147	26,716
Total revenues	53,752	53,318
DP [Member]
Revenues from rental, lease and sale segment
Rentals and leases	4,060	4,707
Sales of equipment and other revenues	689	625
Total revenues	$ 4,749	$ 5,332

Aggregate revenue recognized during the period (derived from goods sold, services rendered, insurance premiums, or other activities that constitute an entity's earning process). For financial services companies, also includes investment and interest income, and sales and trading gains.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration