Goodwill (Details) (USD $)	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Goodwill [Line Items]
Goodwill, Gross	$ 1,412,042,000	$ 1,412,042,000	$ 1,258,917,000	$ 1,092,480,000
Goodwill	1,291,231,000	1,291,231,000	1,237,607,000	1,092,480,000
Goodwill, Translation Adjustments		1,298,000	(14,000)
Goodwill, Translation and Purchase Accounting Adjustments		(4,288,000)	(901,000)
Goodwill, Impairment Loss		(99,501,000)	(21,310,000)	0
Fair Value Inputs, Discount Rate	15.50%
Goodwill Impairment Loss, Net of Tax Benefit		60,600,000
Goodwill, Acquired During Period		156,115,000	167,352,000
Goodwill, Impaired, Accumulated Impairment Loss	120,811,000	120,811,000	(21,310,000)	0
Animal Hospital [Member]
Goodwill [Line Items]
Goodwill, Gross	1,177,348,000	1,177,348,000	1,035,401,000	965,999,000
Goodwill	1,177,348,000	1,177,348,000	1,035,401,000	965,999,000
Goodwill, Translation Adjustments		1,281,000	0
Goodwill, Translation and Purchase Accounting Adjustments		(3,260,000)	(767,000)
Goodwill, Impairment Loss		0	0
Goodwill, Acquired During Period		143,926,000	70,169,000
Goodwill, Impaired, Accumulated Impairment Loss	0	0	0	0
Laboratory [Member]
Goodwill [Line Items]
Goodwill, Gross	96,861,000	96,861,000	96,810,000	96,818,000
Goodwill	96,861,000	96,861,000	96,810,000	96,818,000
Goodwill, Translation Adjustments		17,000	(14,000)
Goodwill, Translation and Purchase Accounting Adjustments		0	0
Goodwill, Impairment Loss		0	0
Goodwill, Acquired During Period		34,000	6,000
Goodwill, Impaired, Accumulated Impairment Loss	0	0	0	0
Other Segments [Member]
Goodwill [Line Items]
Goodwill, Gross	137,833,000	137,833,000	126,706,000	29,663,000
Goodwill	17,022,000	17,022,000	105,396,000	29,663,000
Goodwill, Translation Adjustments		0	0
Goodwill, Translation and Purchase Accounting Adjustments		(1,028,000)	(134,000)
Goodwill, Impairment Loss		(99,501,000)	(21,310,000)
Goodwill, Acquired During Period		12,155,000	97,177,000
Goodwill, Impaired, Accumulated Impairment Loss	$ 120,811,000	$ 120,811,000	$ (21,310,000)	$ 0