Acquisitions Acquisition (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013 Hospital	Mar. 31, 2012 Hospital	Dec. 31, 2012 Hospital
Business Acquisition Summary Of Acquired Properties [Line Items]
Payments (Less Than $1M) To Acquire Real Estate For Use by Owner	$ 510,000
Business Acquisition, Cost of Acquired Entity, Cash Paid	6,756,000	65,273,000
Business Acquisition, Contingent Consideration, at Fair Value	(53,000)	0
Noncontrolling Interest, Increase from Business Combination	0	(6,071,000)
Business Combination, Step Acquisition, Equity Interest in Acquiree, Fair Value	0	(11,850,000)
Animal Hospital [Member]
Business Acquisition Summary Of Acquired Properties [Line Items]
Number of Businesses Acquired	3	9
Number Of Acquired Hospitals Relocated To Existing Hospitals	0	(2)
Number Of Properties Sold Closed Or Merged	(8)	(3)
Change In Number Of Animal Hospitals Owned During The Period	(5)	48
Animal Hospitals And Laboratory Acquisitions [Member]
Business Acquisition Summary Of Acquired Properties [Line Items]
Business Acquisition, Purchase Price Allocation, Goodwill, Expected Tax Deductible Amount	4,100,000	3,400,000
Business Acquisition, Cost of Acquired Entity, Cash Paid	6,756,000	8,988,000
Business Acquisition Cost Of Acquired Entity Cash Paid For Hold Backs	160,000	225,000
Business Acquisition, Contingent Consideration, at Fair Value	53,000	0
Business Combination, Consideration Transferred	6,969,000	9,213,000
Business Acquisition, Purchase Price Allocation, Tangible Assets	491,000	308,000
Business Acquisition, Purchase Price Allocation, Amortizable Intangible Assets	1,506,000	1,616,000
Business Acquisition, Purchase Price Allocation, Goodwill Amount	4,972,000	7,289,000
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net	6,969,000	9,213,000
AVC [Member]
Business Acquisition Summary Of Acquired Properties [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			6 years
Business Acquisition Cost Of Acquired Entity Preliminary Purchase Price			81,000,000
ThinkPetsAcquisition [Member]
Business Acquisition Summary Of Acquired Properties [Line Items]
Business Acquisition, Purchase Price Allocation, Goodwill, Expected Tax Deductible Amount	821,000
Business Acquisition, Cost of Acquired Entity, Cash Paid			7,468,000
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned			10,500,000
Business Acquisition Cost Of Acquired Entity Cash Paid For Hold Backs			1,050,000
Business Combination, Consideration Transferred			19,018,000
Business Acquisition, Purchase Price Allocation, Tangible Assets			2,093,000
Business Acquisition, Purchase Price Allocation, Amortizable Intangible Assets			7,221,000
Business Acquisition, Purchase Price Allocation, Goodwill Amount			12,155,000
Business Acquisition, Purchase Price Allocation, Liabilities Assumed			(2,451,000)
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net			19,018,000
Business Acquisition, Percentage of Voting Interests Acquired			100.00%
Business Acquisition Cost Of Acquired Entity Preliminary Purchase Price			21,000,000
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares			473,389
business acquisition cash including acquired cash			10,500,000
Think Pets Inc [Member]
Business Acquisition Summary Of Acquired Properties [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			8 years
AVC Acquisition [Member]
Business Acquisition Summary Of Acquired Properties [Line Items]
Number of Businesses Acquired	0	44	44
Annualized Revenue At Acquisition CAD			95,000,000
Business Acquisition, Purchase Price Allocation, Goodwill, Expected Tax Deductible Amount	362,000
Preliminary Purchase Price CAD			81,000,000
Business Acquisition, Cost of Acquired Entity, Cash Paid			48,819,000
Business Combination, Consideration Transferred			74,734,000
Business Acquisition, Purchase Price Allocation, Tangible Assets			11,694,000
Business Acquisition, Purchase Price Allocation, Amortizable Intangible Assets			25,170,000
Business Acquisition, Purchase Price Allocation, Goodwill Amount			79,707,000
Business Acquisition, Purchase Price Allocation, Liabilities Assumed			(21,826,000)
business acquisition purchase price allocation total			94,745,000
Noncontrolling Interest, Increase from Business Combination			(8,161,000)
Business Combination, Step Acquisition, Equity Interest in Acquiree, Fair Value			(11,850,000)
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net			74,734,000
Business Acquisitions Cash Paid To Debtholders			25,915,000
US Annualized Revenue At Acquisition			$ 95,000,000
Laboratories Acquisitions [Member]
Business Acquisition Summary Of Acquired Properties [Line Items]
Number of Businesses Acquired	1	0
Customer Relationships [Member] | AVC [Member]
Business Acquisition Summary Of Acquired Properties [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			5 years
Customer Relationships [Member] | Think Pets Inc [Member]
Business Acquisition Summary Of Acquired Properties [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			9 years
Technology And Trademarks [Member] | Think Pets Inc [Member]
Business Acquisition Summary Of Acquired Properties [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			4 years
Trademarks [Member] | AVC [Member]
Business Acquisition Summary Of Acquired Properties [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			10 years
Trademarks [Member] | Think Pets Inc [Member]
Business Acquisition Summary Of Acquired Properties [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			2 years
Noncompete Agreements [Member] | AVC [Member]
Business Acquisition Summary Of Acquired Properties [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			3 years