Note 15 - Segment and Geographic Information (Detail) - Sales by Product Group (USD $) In Thousands, unless otherwise specified	3 Months Ended			6 Months Ended	9 Months Ended
	Feb. 28, 2013	Feb. 29, 2012	Aug. 19, 2011	Feb. 29, 2012	Feb. 28, 2013
Net sales by product group:
Sales by product group	$ 86,192	$ 81,370	$ 74,910	$ 175,795	$ 253,402
Traditional Reagents [Member]
Net sales by product group:
Sales by product group	46,100	48,371	42,936	102,362	139,143
Capture Reagents [Member]
Net sales by product group:
Sales by product group	24,151	20,153	21,239	45,801	69,263
Instruments [Member]
Net sales by product group:
Sales by product group	14,243	11,362	9,457	24,439	40,020
Molecular Immunohematology [Member]
Net sales by product group:
Sales by product group	$ 1,698	$ 1,484	$ 1,278	$ 3,193	$ 4,976