Goodwill and Other Intangible Assets Goodwill and Other Intangible Assets (Details) (USD $)	6 Months Ended
	Jun. 30, 2012
Goodwill [Line Items]
Goodwill, Impaired, Accumulated Impairment Loss	$ 21,300,000
Goodwill, Beginning Balance	1,237,607,000
Goodwill acquired	113,396,000
Other	(5,474,000)
Goodwill, Ending Balance	1,345,529,000
Goodwill, Impairment Loss	0
Animal Hospital [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	1,035,401,000
Goodwill acquired	102,819,000
Other	(5,104,000)
Goodwill, Ending Balance	1,133,116,000
Laboratory [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	96,810,000
Goodwill acquired	8,000
Other	2,000
Goodwill, Ending Balance	96,820,000
All Other [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	105,396,000
Goodwill acquired	10,569,000
Other	(372,000)
Goodwill, Ending Balance	$ 115,593,000