Segment Reporting (Summary Of Revenue By Product And Service Category) (Details) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Revenue	$ 300,954	$ 269,628	$ 911,488	$ 819,635
Companion Animal Group [Member]
Revenue	248,074	222,909	748,397	676,646
Companion Animal Group [Member] | Instruments And Consumables [Member]
Revenue	99,719	88,481	292,209	258,318
Companion Animal Group [Member] | Rapid Assay Products [Member]
Revenue	36,073	35,576	118,883	115,500
Companion Animal Group [Member] | Reference Laboratory Diagnostic And Consulting Services [Member]
Revenue	94,027	82,534	282,242	248,422
Companion Animal Group [Member] | Practice Management Systems And Digital Radiography [Member]
Revenue	18,255	16,318	55,063	54,406
Water [Member]
Revenue	21,648	20,044	62,123	57,356
Livestock And Poultry Diagnostics [Member]
Revenue	20,675	17,476	69,981	56,577
Other [Member]
Revenue	$ 10,557	$ 9,199	$ 30,987	$ 29,056