Goodwill and Other Intangible Assets (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Goodwill
Goodwill, Beginning Balance			$ 1,092,480
Goodwill acquired			10,352
Other			(1,974)
Goodwill, Ending Balance	1,100,858		1,100,858
Other Intangible Assets
Gross Carrying Amount	73,079		73,079		74,604
Accumulated Amortization	(29,454)		(29,454)		(27,618)
Net Carrying Amount	43,625		43,625		46,986
Aggregate amortization expense
Aggregate amortization expense	2,604	2,187	5,259	4,341
Estimated amortization expense related to intangible assets
Remainder of 2011			5,322
2012			9,901
2013			7,669
2014			5,411
2015			3,560
Thereafter			11,762
Total			43,625
Goodwill and Other Intangible Assets (Textuals) [Abstract]
Accumulated impairment losses	0		0
Animal Hospital [Member]
Goodwill
Goodwill, Beginning Balance			965,999
Goodwill acquired			10,346
Other			(1,862)
Goodwill, Ending Balance	974,483		974,483
Laboratory [Member]
Goodwill
Goodwill, Beginning Balance			96,818
Goodwill acquired			6
Other			22
Goodwill, Ending Balance	96,846		96,846
Medical Technology [Member]
Goodwill
Goodwill, Beginning Balance			29,663
Other			(134)
Goodwill, Ending Balance	29,529		29,529
Noncontractual customer relationships [Member]
Other Intangible Assets
Gross Carrying Amount	48,319		48,319		48,686
Accumulated Amortization	(15,791)		(15,791)		(14,188)
Net Carrying Amount	32,528		32,528		34,498
Covenants not-to-compete [Member]
Other Intangible Assets
Gross Carrying Amount	13,285		13,285		14,459
Accumulated Amortization	(7,961)		(7,961)		(8,311)
Net Carrying Amount	5,324		5,324		6,148
Favorable lease asset [Member]
Other Intangible Assets
Gross Carrying Amount	5,486		5,486		5,486
Accumulated Amortization	(2,940)		(2,940)		(2,672)
Net Carrying Amount	2,546		2,546		2,814
Trademarks [Member]
Other Intangible Assets
Gross Carrying Amount	3,716		3,716		3,749
Accumulated Amortization	(1,227)		(1,227)		(986)
Net Carrying Amount	2,489		2,489		2,763
Technology [Member]
Other Intangible Assets
Gross Carrying Amount	2,189		2,189		2,189
Accumulated Amortization	(1,514)		(1,514)		(1,447)
Net Carrying Amount	675		675		742
Client lists [Member]
Other Intangible Assets
Gross Carrying Amount	84		84		35
Accumulated Amortization	(21)		(21)		(14)
Net Carrying Amount	$ 63		$ 63		$ 21