Segment Reporting (Summary Of Revenue By Product And Service Category) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Revenue	$ 351,959	$ 383,523	$ 390,122	$ 360,203	$ 354,073	$ 338,297	$ 352,583	$ 332,106	$ 1,485,807	$ 1,377,058	$ 1,293,338
CAG Segment [Member]
Segment Reporting Information [Line Items]
Revenue									1,236,855	1,150,169	1,072,211
CAG Segment [Member] | CAG Diagnostics Recurring Revenue [Member]
Segment Reporting Information [Line Items]
Revenue									1,053,410	973,886	896,449
CAG Segment [Member] | Vetlab Consumables [Member]
Segment Reporting Information [Line Items]
Revenue									341,397	312,457	278,818
CAG Segment [Member] | VetLab Service and Accessories [Member]
Segment Reporting Information [Line Items]
Revenue									53,383	50,675	48,056
CAG Segment [Member] | Rapid Assay Products [Member]
Segment Reporting Information [Line Items]
Revenue									165,647	169,547	162,232
CAG Segment [Member] | Reference Laboratory Diagnostic And Consulting Services [Member]
Segment Reporting Information [Line Items]
Revenue									492,983	441,207	407,343
CAG Segment [Member] | CAG Diagnostic Capital - Instruments [Member]
Segment Reporting Information [Line Items]
Revenue									79,626	83,492	90,177
CAG Segment [Member] | Customer Information Managment and Digital Imaging Systems [Member]
Segment Reporting Information [Line Items]
Revenue									103,819	92,791	85,585
Water Segment [Member]
Segment Reporting Information [Line Items]
Revenue									94,725	87,959	84,680
LPD Segment [Member]
Segment Reporting Information [Line Items]
Revenue									127,388	113,811	111,308
Other Segment [Member]
Segment Reporting Information [Line Items]
Revenue									$ 26,839	$ 25,119	$ 25,139