Goodwill and Other Intangible Assets Goodwill and Other Intangible Assets (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Goodwill [Line Items]
Future Amortization Expense, Remainder of Fiscal Year	$ 5,471,000		$ 5,471,000
Finite-Lived Intangible Assets, Amortization Expense	5,588,000	6,612,000	16,153,000	16,830,000
Finite-Lived Intangible Assets, Gross	148,914,000	150,427,000	148,914,000	150,427,000
Goodwill, Impaired, Accumulated Impairment Loss	(120,811,000)		(120,811,000)		(120,811,000)
Goodwill, Gross	1,441,763,000		1,441,763,000		1,412,042,000
Goodwill, Beginning Balance			1,291,231,000
Goodwill acquired			32,557,000
Goodwill, Translation Adjustments			(2,858,000)
Other			22,000
Goodwill, Ending Balance	1,320,952,000		1,320,952,000
Finite-Lived Intangible Assets, Accumulated Amortization	(58,775,000)	(55,604,000)	(58,775,000)	(55,604,000)
Finite-Lived Intangible Assets, Net	90,139,000	94,823,000	90,139,000	94,823,000	94,823,000
Future Amortization Expense, Year One	20,613,000		20,613,000
Future Amortization Expense, Year Two	18,557,000		18,557,000
Future Amortization Expense, Year Three	15,520,000		15,520,000
Future Amortization Expense, Year Four	9,096,000		9,096,000
Future Amortization Expense, after Year Five	20,882,000		20,882,000
Animal Hospital [Member]
Goodwill [Line Items]
Goodwill, Impaired, Accumulated Impairment Loss	0		0		0
Goodwill, Gross	1,206,640,000		1,206,640,000		1,177,348,000
Goodwill, Beginning Balance			1,177,348,000
Goodwill acquired			32,549,000
Goodwill, Translation Adjustments	(2,836,000)
Other			(421,000)
Goodwill, Ending Balance	1,206,640,000		1,206,640,000
All Other Segments [Member]
Goodwill [Line Items]
Goodwill, Impaired, Accumulated Impairment Loss	(120,811,000)		(120,811,000)		(120,811,000)
Goodwill, Beginning Balance					17,022,000
Goodwill, Ending Balance	17,465,000		17,465,000		17,022,000
Laboratory [Member]
Goodwill [Line Items]
Goodwill, Impaired, Accumulated Impairment Loss	0		0		0
Goodwill, Gross	96,847,000		96,847,000		96,861,000
Goodwill, Beginning Balance			96,861,000
Goodwill acquired			8,000
Goodwill, Translation Adjustments			(22,000)
Other			0
Goodwill, Ending Balance	96,847,000		96,847,000
All Other [Member]
Goodwill [Line Items]
Goodwill, Gross	138,276,000		138,276,000		137,833,000
Goodwill acquired			0
Goodwill, Translation Adjustments			0
Other			443,000
Customer Lists [Member]
Goodwill [Line Items]
Finite-Lived Intangible Assets, Gross	50,000	50,000	50,000	50,000
Finite-Lived Intangible Assets, Accumulated Amortization	(39,000)	(26,000)	(39,000)	(26,000)
Finite-Lived Intangible Assets, Net	11,000	24,000	11,000	24,000
Contract [Member]
Goodwill [Line Items]
Finite-Lived Intangible Assets, Gross	956,000	956,000	956,000	956,000
Finite-Lived Intangible Assets, Accumulated Amortization	(633,000)	(570,000)	(633,000)	(570,000)
Finite-Lived Intangible Assets, Net	323,000	386,000	323,000	386,000
Trademarks [Member]
Goodwill [Line Items]
Finite-Lived Intangible Assets, Gross	12,096,000	12,494,000	12,096,000	12,494,000
Finite-Lived Intangible Assets, Accumulated Amortization	(3,865,000)	(3,001,000)	(3,865,000)	(3,001,000)
Finite-Lived Intangible Assets, Net	8,231,000	9,493,000	8,231,000	9,493,000
Lease Agreements [Member]
Goodwill [Line Items]
Finite-Lived Intangible Assets, Gross	7,465,000	7,228,000	7,465,000	7,228,000
Finite-Lived Intangible Assets, Accumulated Amortization	(4,252,000)	(3,866,000)	(4,252,000)	(3,866,000)
Finite-Lived Intangible Assets, Net	3,213,000	3,362,000	3,213,000	3,362,000
Noncompete Agreements [Member]
Goodwill [Line Items]
Finite-Lived Intangible Assets, Gross	9,873,000	12,707,000	9,873,000	12,707,000
Finite-Lived Intangible Assets, Accumulated Amortization	(5,458,000)	(7,357,000)	(5,458,000)	(7,357,000)
Finite-Lived Intangible Assets, Net	4,415,000	5,350,000	4,415,000	5,350,000
Developed Technology Rights [Member]
Goodwill [Line Items]
Finite-Lived Intangible Assets, Gross	4,901,000	6,588,000	4,901,000	6,588,000
Finite-Lived Intangible Assets, Accumulated Amortization	(2,891,000)	(4,179,000)	(2,891,000)	(4,179,000)
Finite-Lived Intangible Assets, Net	2,010,000	2,409,000	2,010,000	2,409,000
Customer Relationships [Member]
Goodwill [Line Items]
Finite-Lived Intangible Assets, Gross	113,573,000	110,404,000	113,573,000	110,404,000
Finite-Lived Intangible Assets, Accumulated Amortization	(41,637,000)	(36,605,000)	(41,637,000)	(36,605,000)
Finite-Lived Intangible Assets, Net	$ 71,936,000	$ 73,799,000	$ 71,936,000	$ 73,799,000