Note 15 - Segment and Geographic Information (Detail) - Sales by Product Group (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Nov. 30, 2012	Nov. 30, 2011	Aug. 19, 2011	Nov. 30, 2011	Nov. 30, 2012
Sales by product group
Sales by product group	$ 82,056	$ 83,035	$ 74,910	$ 94,425	$ 167,210
Traditional Reagents [Member]
Sales by product group
Sales by product group	45,996	47,696	42,936	53,991	93,042
Capture Reagents [Member]
Sales by product group
Sales by product group	20,799	22,393	21,239	25,648	45,112
Instruments [Member]
Sales by product group
Sales by product group	13,567	11,458	9,457	13,077	25,777
Molecular Immunohematology [Member]
Sales by product group
Sales by product group	$ 1,694	$ 1,488	$ 1,278	$ 1,709	$ 3,279