Note 15 - Segment and Geographic Information (Details) - Sales by Product Group (USD $) In Thousands, unless otherwise specified	3 Months Ended
Aug. 31, 2014	Aug. 31, 2013
Net sales by product group:
Net sales by product group	$ 102,441	$ 96,044
Transfusion [Member]
Net sales by product group:
Net sales by product group	86,369	82,990
Transplant & Molecular [Member]
Net sales by product group:
Net sales by product group	$ 16,072	$ 13,054

Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

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=26872669&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

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