Acquisitions - Acquisition and Disposal Activity (Details)	9 Months Ended
	Sep. 30, 2016 Laboratory Hospital	Sep. 30, 2015 Laboratory Hospital
Animal Hospital
Business Acquisition Summary Of Acquired Properties [Line Items]
Acquisitions	105	42
Acquisitions, merged	(3)	(4)
Sold, closed or merged	(8)	(7)
Net increase	94	31
Laboratories Acquisitions
Business Acquisition Summary Of Acquired Properties [Line Items]
Acquisitions | Laboratory	0	1
Acquisitions, merged | Laboratory	0	(1)
Net increase | Laboratory	0	0