Supplemental Cash Flow Information (Details Textual) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Aug. 31, 2012	Aug. 31, 2011
Rental and lease equipment [Member]
Supplemental Cash Flow Information (Textual) [Abstract]
Accounts payable related to acquired rental and lease equipment	$ 3,448	$ 5,308
Demonstration Equipment [Member]
Supplemental Cash Flow Information (Textual) [Abstract]
Transferred demonstration equipment to rental and lease equipment during the period	$ 1,623	$ 79

Future cash outflow to pay for purchases of fixed assets that have occurred.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586

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