Note 15 - Segment and Geographic Information - Sales by Product Group (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Nov. 30, 2016	Nov. 30, 2015	Nov. 30, 2016	Nov. 30, 2015
Net sales by product group:
Net sales	$ 93,676	$ 96,249	$ 192,269	$ 192,961
Transfusion [Member]
Net sales by product group:
Net sales	76,622	80,521	158,285	161,710
Transplant & Molecular [Member]
Net sales by product group:
Net sales	$ 17,054	$ 15,728	$ 33,984	$ 31,251

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=63488584&loc=d3e20235-122688

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