Segment Reporting (Summary Of Revenue By Product And Service Category) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Segment Reporting Information [Line Items]
Revenue	$ 332,106	$ 322,676
VetLab Instruments and Consumables [Member]
Segment Reporting Information [Line Items]
Revenue	103,671	101,997
Rapid Assay Products [Member]
Segment Reporting Information [Line Items]
Revenue	44,083	43,664
Reference Laboratory Diagnostic And Consulting Services [Member]
Segment Reporting Information [Line Items]
Revenue	107,649	101,862
Practice Management and Digital Imaging Systems and Services [Member]
Segment Reporting Information [Line Items]
Revenue	21,538	20,550
CAG Segment [Member]
Segment Reporting Information [Line Items]
Revenue	276,941	268,073
Water Segment [Member]
Segment Reporting Information [Line Items]
Revenue	20,666	19,582
LPD Segment [Member]
Segment Reporting Information [Line Items]
Revenue	28,039	29,116
Other Segment [Member]
Segment Reporting Information [Line Items]
Revenue	$ 6,460	$ 5,905