Acquisitions (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Business Acquisition [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares	473,389
Cash payment made for acquisitions	$ 5,337,000	$ 1,900,000	$ 9,289,000
Vetstreet [Member]
Business Acquisition [Line Items]
Percentage of Company acquired		100.00%
Weighted average amortization period of identifiable intangible assets		9 years
Business Acquisition, Cost of Acquired Entity, Purchase Price		146,400,000
Pet DRx [Member]
Business Acquisition [Line Items]
Amount of goodwill deducted for income tax purpose			6,400,000
Percentage of Company acquired			70.40%
Number of Businesses Acquired	0	0	23
Business Acquisition, Cost of Acquired Entity, Purchase Price			41,300,000
Bright Heart [Member]
Business Acquisition [Line Items]
Amount of goodwill deducted for income tax purpose		40,700,000
Percentage of Company acquired		100.00%
Weighted average amortization period of identifiable intangible assets		5 years
Number of Businesses Acquired	0	9	0
Business Acquisition, Cost of Acquired Entity, Purchase Price		50,000,000
Pro forma [Member]
Business Acquisition [Line Items]
Acquisition related costs	1,500,000
Think Pets Inc [Member]
Business Acquisition [Line Items]
Amount of goodwill deducted for income tax purpose	821,000
Percentage of Company acquired	100.00%
Preliminary purchase price, net of cash acquired	21,000,000
Weighted average amortization period of identifiable intangible assets	8 years
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned	10,500,000
AVC [Member]
Business Acquisition [Line Items]
Amount of goodwill deducted for income tax purpose	362,000
US Annualized Revenue At Acquisition	95,000,000
Annualized Revenue At Acquisition CAD	95,000,000
Preliminary purchase price, net of cash acquired	81,000,000
Preliminary Purchase Price CAD	81,000,000
Weighted average amortization period of identifiable intangible assets	6 years
Number of Businesses Acquired	44	0	0
Acquisitions Excluding Bright Heart And Pet DRx [Member]
Business Acquisition [Line Items]
Amount of goodwill deducted for income tax purpose	$ 60,400,000	$ 26,400,000	$ 58,200,000
Number of Businesses Acquired	35	18	27
Noncompete Agreements [Member] | Vetstreet [Member]
Business Acquisition [Line Items]
Weighted average amortization period of identifiable intangible assets		2 years
Noncompete Agreements [Member] | AVC [Member]
Business Acquisition [Line Items]
Weighted average amortization period of identifiable intangible assets	3 years
Contracts [Member] | Vetstreet [Member]
Business Acquisition [Line Items]
Weighted average amortization period of identifiable intangible assets		8 years
Customer Relationships [Member] | Vetstreet [Member]
Business Acquisition [Line Items]
Weighted average amortization period of identifiable intangible assets		10 years
Customer Relationships [Member] | Think Pets Inc [Member]
Business Acquisition [Line Items]
Weighted average amortization period of identifiable intangible assets	9 years
Customer Relationships [Member] | AVC [Member]
Business Acquisition [Line Items]
Weighted average amortization period of identifiable intangible assets	5 years
Technology And Trademarks [Member] | Vetstreet [Member]
Business Acquisition [Line Items]
Weighted average amortization period of identifiable intangible assets		7 years
Technology And Trademarks [Member] | Think Pets Inc [Member]
Business Acquisition [Line Items]
Weighted average amortization period of identifiable intangible assets	4 years
Trademarks [Member] | Think Pets Inc [Member]
Business Acquisition [Line Items]
Weighted average amortization period of identifiable intangible assets	2 years
Trademarks [Member] | AVC [Member]
Business Acquisition [Line Items]
Weighted average amortization period of identifiable intangible assets	10 years