Note 16 - Segment and Geographic Information (Details) - Sales by Product Group (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Feb. 28, 2015	Feb. 28, 2014	Feb. 28, 2015	Feb. 28, 2014
Net sales by product group:
Net sales by product group	$ 95,605	$ 90,979	$ 294,323	$ 287,226
Transfusion [Member]
Net sales by product group:
Net sales by product group	79,929	77,381	247,950	245,930
Transplant & Molecular [Member]
Net sales by product group:
Net sales by product group	$ 15,676	$ 13,598	$ 46,373	$ 41,296