Summary of Significant Accounting Policies (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Goodwill
Goodwill, Beginning Balance	$ 1,092,480	$ 985,674
Goodwill acquired	167,352	105,801
Goodwill impairment	(21,310)
Other	(915)	1,005
Goodwill, Ending Balance	1,237,607	1,092,480
Animal Hospital [Member]
Goodwill
Goodwill, Beginning Balance	965,999	861,868
Goodwill acquired	70,169	105,794
Other	(767)	(1,663)
Goodwill, Ending Balance	1,035,401	965,999
Laboratory [Member]
Goodwill
Goodwill, Beginning Balance	96,818	96,285
Goodwill acquired	6	7
Other	(14)	526
Goodwill, Ending Balance	96,810	96,818
All Other [Member]
Goodwill
Goodwill, Beginning Balance	29,663	27,521
Goodwill acquired	97,177
Goodwill impairment	(21,310)
Other	(134)	2,142
Goodwill, Ending Balance	$ 105,396	$ 29,663