Note 18. Segment and Geographic Information (Detail) - Sales by Product Group (USD $) In Thousands, unless otherwise specified	3 Months Ended								9 Months Ended	12 Months Ended
	May 31, 2012	Feb. 29, 2012	Nov. 30, 2011	Aug. 19, 2011	May 31, 2011	Feb. 28, 2011	Nov. 30, 2010	Aug. 31, 2010	May 31, 2012	Aug. 31, 2012	May 31, 2011	May 31, 2010
Sales by product group	$ 86,019	$ 81,370	$ 83,035	$ 74,910	$ 84,555	$ 83,349	$ 81,546	$ 83,641	$ 261,814	$ 11,390	$ 333,091	$ 329,073
Traditional Reagents [Member]
Sales by product group				42,936					151,644		199,826	207,710
Capture Reagents [Member]
Sales by product group				21,239					69,174		82,366	77,003
Instruments [Member]
Sales by product group				9,457					36,228		45,112	39,680
Molecular Immunohematology [Member]
Sales by product group				$ 1,278					$ 4,768		$ 5,787	$ 4,680