Goodwill and Other Intangible Assets (Details 1) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Goodwill, Acquired During Period			$ 20,979,000
Other Intangible Assets
Gross Carrying Amount	143,403,000	150,427,000	143,403,000	150,427,000
Accumulated Amortization	(56,672,000)	(55,604,000)	(56,672,000)	(55,604,000)
Total	86,731,000	94,823,000	86,731,000	94,823,000	94,823,000
Aggregate amortization expense	5,521,000	5,342,000	10,565,000	10,218,000
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Remainder of 2012	10,051,000		10,051,000
2013	18,537,000		18,537,000
2014	16,499,000		16,499,000
2015	13,474,000		13,474,000
2016	7,118,000		7,118,000
Thereafter	21,052,000		21,052,000
Total	86,731,000	94,823,000	86,731,000	94,823,000	94,823,000
Goodwill and Other Intangible Assets (Textuals) [Abstract]
Accumulated impairment losses	(120,811,000)		(120,811,000)		(120,811,000)
Noncontractual customer relationships [Member]
Other Intangible Assets
Gross Carrying Amount	104,775,000	110,404,000	104,775,000	110,404,000
Accumulated Amortization	(37,830,000)	(36,605,000)	(37,830,000)	(36,605,000)
Total	66,945,000	73,799,000	66,945,000	73,799,000
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Total	66,945,000	73,799,000	66,945,000	73,799,000
Covenants not-to-compete [Member]
Other Intangible Assets
Gross Carrying Amount	10,502,000	12,707,000	10,502,000	12,707,000
Accumulated Amortization	(6,036,000)	(7,357,000)	(6,036,000)	(7,357,000)
Total	4,466,000	5,350,000	4,466,000	5,350,000
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Total	4,466,000	5,350,000	4,466,000	5,350,000
Favorable lease asset [Member]
Other Intangible Assets
Gross Carrying Amount	8,559,000	7,228,000	8,559,000	7,228,000
Accumulated Amortization	(4,157,000)	(3,866,000)	(4,157,000)	(3,866,000)
Total	4,402,000	3,362,000	4,402,000	3,362,000
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Total	4,402,000	3,362,000	4,402,000	3,362,000
Trademarks [Member]
Other Intangible Assets
Gross Carrying Amount	11,973,000	12,494,000	11,973,000	12,494,000
Accumulated Amortization	(3,557,000)	(3,001,000)	(3,557,000)	(3,001,000)
Total	8,416,000	9,493,000	8,416,000	9,493,000
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Total	8,416,000	9,493,000	8,416,000	9,493,000
Contracts [Member]
Other Intangible Assets
Gross Carrying Amount	956,000	956,000	956,000	956,000
Accumulated Amortization	(612,000)	(570,000)	(612,000)	(570,000)
Total	344,000	386,000	344,000	386,000
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Total	344,000	386,000	344,000	386,000
Technology [Member]
Other Intangible Assets
Gross Carrying Amount	6,588,000	6,588,000	6,588,000	6,588,000
Accumulated Amortization	(4,445,000)	(4,179,000)	(4,445,000)	(4,179,000)
Total	2,143,000	2,409,000	2,143,000	2,409,000
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Total	2,143,000	2,409,000	2,143,000	2,409,000
Client lists [Member]
Other Intangible Assets
Gross Carrying Amount	50,000	50,000	50,000	50,000
Accumulated Amortization	(35,000)	(26,000)	(35,000)	(26,000)
Total	15,000	24,000	15,000	24,000
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Total	15,000	24,000	15,000	24,000
Laboratory [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill, Acquired During Period			8,000
Goodwill and Other Intangible Assets (Textuals) [Abstract]
Accumulated impairment losses	0		0		0
All Other [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill, Acquired During Period			0
Animal Hospital [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill, Acquired During Period			20,971,000
Goodwill and Other Intangible Assets (Textuals) [Abstract]
Accumulated impairment losses	0		0		0
Animal Hospitals And Laboratory Acquisitions [Member]
Finite-Lived Intangible Assets [Line Items]
Business Acquisition, Purchase Price Allocation, Goodwill, Expected Tax Deductible Amount	$ 20,200,000	$ 11,800,000	$ 20,200,000	$ 11,800,000