Acquisitions (Details) $ in Thousands			9 Months Ended
		Aug. 15, 2014 USD ($)	Sep. 30, 2015 USD ($) Laboratory Hospital	Sep. 30, 2014 USD ($) Laboratory Hospital	Dec. 31, 2014 USD ($)
Consideration:
Cash, net of cash acquired			$ 119,336	$ 65,415
Earn-outs			3,100		$ 3,200
Allocation of the Purchase Price:
Goodwill			1,489,843		$ 1,415,861
Fair value of pre-existing investment			0	(2,014)
Animal Hospitals And Laboratory Acquisitions [Member]
Consideration:
Cash, net of cash acquired			119,036	46,948
Assumed debt			12,402	4,160
Holdbacks			4,497	1,400
Earn-outs			476	721
Fair value of total consideration transferred			136,411	53,229
Allocation of the Purchase Price:
Tangible assets			10,060	2,317
Identifiable intangible assets	[1]		34,130	8,176
Goodwill	[2]		93,645	46,502
Other liabilities assumed			(1,424)	(47)
Fair value of assets acquired and liabilities assumed			136,411	56,948
Noncontrolling interest			0	(1,705)
Fair value of pre-existing investment			0	(2,014)
Total			$ 136,411	53,229
Weighted average useful life (in years)			12 years
Goodwill recorded for acquisitions, fully deductible for income tax purposes			$ 73,800	$ 36,600
Animal Hospital [Member]
Business Acquisition Summary Of Acquired Properties [Line Items]
Acquisitions | Hospital			42	23
Acquisitions, merged | Hospital			(4)	(4)
Sold, closed or merged | Hospital			(7)	(6)
Net increase | Hospital			31	13
Laboratories Acquisitions [Member]
Business Acquisition Summary Of Acquired Properties [Line Items]
Acquisitions | Laboratory			1	0
Acquisitions, merged | Laboratory			(1)	0
New facilities | Laboratory			0	3
Net increase | Laboratory			0	3
D.O.G. Enterprises, LLC [Member]
Consideration:
Cash, net of cash acquired		$ 15,174
Assumed debt		323
Holdbacks		1,500
Earn-outs		760
Fair value of total consideration transferred		17,757
Allocation of the Purchase Price:
Tangible assets		637
Identifiable intangible assets	[3]	13,420
Goodwill	[4]	4,219
Other liabilities assumed		(519)
Total		$ 17,757
Weighted average useful life (in years)		10 years
Customer Relationships [Member] | Animal Hospitals And Laboratory Acquisitions [Member]
Allocation of the Purchase Price:
Weighted average useful life (in years)			13 years
Trademarks [Member] | Animal Hospitals And Laboratory Acquisitions [Member]
Allocation of the Purchase Price:
Weighted average useful life (in years)			9 years
Franchise rights [Member] | D.O.G. Enterprises, LLC [Member]
Allocation of the Purchase Price:
Weighted average useful life (in years)		10 years
Covenants [Member] | Animal Hospitals And Laboratory Acquisitions [Member]
Allocation of the Purchase Price:
Weighted average useful life (in years)			5 years
Covenants [Member] | D.O.G. Enterprises, LLC [Member]
Allocation of the Purchase Price:
Weighted average useful life (in years)		3 years
Existing Technology [Member] | D.O.G. Enterprises, LLC [Member]
Allocation of the Purchase Price:
Weighted average useful life (in years)		4 years

[1] Identifiable intangible assets include customer relationships, trademarks and covenants-not-to-compete. The weighted-average amortization period for the total identifiable intangible assets is approximately twelve years. The weighted-average amortization period for customer relationships, trademarks and covenants is approximately thirteen years, nine years and five years, respectively.

[2] We expect that $73.8 million and $36.6 million of the goodwill recorded for these acquisitions, as of September 30, 2015 and 2014, respectively, will be fully deductible for income tax purposes.

[3] Identifiable intangible assets primarily include franchise rights, trademarks, covenants-not-to-compete and existing technology. The weighted-average amortization period for the total identifiable intangible assets is approximately ten years. The weighted-average amortization periods for the franchise rights, covenants and existing technology is approximately ten years, three years and four years, respectively. The trademarks have an indefinite life and will be assessed annually for impairment.

[4] As of September 30, 2015, we expect that the full amount of goodwill recorded for this acquisition will be deductible for income tax purposes.