Acquisitions - Acquisition and Disposal Activity (Details)	6 Months Ended
	Jun. 30, 2017 Laboratory Hospital	Jun. 30, 2016 Laboratory Hospital	May 01, 2016
Animal Hospitals, Excluding CAPNA
Business Acquisition Summary Of Acquired Properties [Line Items]
Acquisitions	24	37
Companion Animal Practices, North America
Business Acquisition Summary Of Acquired Properties [Line Items]
Acquisitions	0	56
Percentage of ownership interest			80.00%
Animal Hospital
Business Acquisition Summary Of Acquired Properties [Line Items]
Acquisitions, merged	(2)	(3)
Sold, closed or merged	(5)	(5)
Net increase	17	85
Laboratories
Business Acquisition Summary Of Acquired Properties [Line Items]
New facilities | Laboratory	1	0
Net increase | Laboratory	1	0