Acquisitions (Details 1) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	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]	Jul. 11, 2011 BrightHeart [Member]	Dec. 31, 2011 MediMedia Animal Health, LLC (Vetstreet) [Member]
Consideration:
Cash paid for acquisitions	$ (203,996)	$ (79,851)	$ (74,567)	$ 34,243	$ 69,456	$ 56,806	$ 23,490	$ 50,000	$ 146,420
Non-cash note conversion to equity interest in subsidiary				0		5,700
Contingent consideration	560	259	712	79	2,857	712	481
Cash paid to holders of debt							26,048
Cash paid for holdbacks				1,500
Fair value of total consideration transferred				35,822	72,313	63,218	50,019
Allocation of the Purchase Price:
Tangible assets				1,237	3,592	8,625	21,129		7,861
Identifiable intangible assets				6,414	9,510	9,408	7,205		45,810
Goodwill				28,171	60,839	51,171	42,004		97,177
Notes payable and other liabilities assumed				0	(1,628)	(5,986)	(20,319)		(4,428)
Total				$ 35,822	$ 72,313	$ 63,218	$ 50,019		$ 146,420