Acquisitions (Details Textual) (USD $)	12 Months Ended												1 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Customer Relationships [Member] Y	Dec. 31, 2011 Technology And Trademarks [Member] Y	Dec. 31, 2011 Non Compete Agreements [Member] Y	Dec. 31, 2011 Contracts [Member] Y	Dec. 31, 2011 Animal Hospitals and Laboratory Acquisitions [Member]	Dec. 31, 2010 Animal Hospitals and Laboratory Acquisitions [Member]	Dec. 31, 2009 Animal Hospitals and Laboratory Acquisitions [Member]	Dec. 31, 2011 BrightHeart [Member] Hospitals Y	Jul. 11, 2011 BrightHeart [Member]	Aug. 09, 2011 MediMedia Animal Health, LLC (Vetstreet) [Member]	Dec. 31, 2011 MediMedia Animal Health, LLC (Vetstreet) [Member] Y
Business Acquisition [Line Items]
Amount of goodwill deducted for income tax purpose								$ 26,400,000	$ 58,200,000	$ 33,600,000	$ 40,700,000			$ 0
Cash payment made for acquisitions	1,900,000	9,289,000	4,894,000					1,900,000	9,300,000	4,900,000	1,300,000
Cash paid for acquisitions	(203,996,000)	(79,851,000)	(74,567,000)					34,243,000	69,456,000	56,806,000	23,490,000	50,000,000		146,420,000
Cash Acquired from Acquisition													0
Preliminary purchase price, net of cash acquired													146,400,000
Number of animal hospitals											9
Number of animal hospitals which focus on the delivery of specialty and emergency medicine											8
Weighted average amortization period of identifiable intangible assets				10	7	2	8				5			9
Percentage of Company acquired												100.00%	100.00%
Acquisition related costs														1,200,000
Acquisitions (Textual) [Abstract]
Acquisition-related costs excluded from 2011 supplemental pro forma net income	$ 2,500,000