Acquisitions - Companion Animal Practices, North America Acquisition (Details) $ in Thousands		9 Months Ended
	May 01, 2016 USD ($) Hospital State	Sep. 30, 2016 USD ($) Hospital State	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Business Acquisition [Line Items]
Number of hospitals operated | Hospital		776
Number of states in which hospitals are operated | State		43
Consideration:
Cash, net of cash acquired		$ 599,655	$ 119,336
Allocation of the Purchase Price:
Goodwill		2,063,494		$ 1,517,650
Companion Animal Practices, North America
Business Acquisition [Line Items]
Percentage of ownership interest	80.00%
Number of hospitals operated | Hospital	56
Number of states in which hospitals are operated | State	18
Consideration:
Cash	$ 352,829
Cash acquired	(3,405)
Cash, net of cash acquired	349,424
Holdbacks	1,000
Fair value of total consideration transferred	350,424
Allocation of the Purchase Price:
Tangible assets	21,118
Identifiable intangible assets	102,300
Goodwill	330,668
Other liabilities assumed	(17,662)
Fair value of assets acquired and liabilities assumed	436,424
Noncontrolling interest	(86,000)
Total	$ 350,424
Weighted average amortization period	7 years
Goodwill recorded for acquisitions, fully deductible for income tax purposes		$ 265,800
Companion Animal Practices, North America | Customer Relationships
Allocation of the Purchase Price:
Weighted average amortization period	7 years
Companion Animal Practices, North America | Trademarks
Allocation of the Purchase Price:
Weighted average amortization period	5 years
Companion Animal Practices, North America | Covenants
Allocation of the Purchase Price:
Weighted average amortization period	5 years