Summary of Significant Accounting Policies - Estimated Useful Lives of Intangibles (Details)	12 Months Ended
	Dec. 31, 2016
Client List
Amortization of intangible assets estimated useful lives
Amortization of intangible assets estimated useful lives	3 years
Franchise rights
Amortization of intangible assets estimated useful lives
Amortization of intangible assets estimated useful lives	10 years
All Other | Non-contractual customer relationships
Amortization of intangible assets estimated useful lives
Amortization of intangible assets estimated useful lives	5 years
Minimum | Covenants not-to-compete
Amortization of intangible assets estimated useful lives
Amortization of intangible assets estimated useful lives	3 years
Minimum | Favorable lease assets
Amortization of intangible assets estimated useful lives
Amortization of intangible assets estimated useful lives	8 years
Minimum | Technology
Amortization of intangible assets estimated useful lives
Amortization of intangible assets estimated useful lives	4 years
Minimum | Trademarks
Amortization of intangible assets estimated useful lives
Amortization of intangible assets estimated useful lives	2 years
Minimum | Animal Hospital | Non-contractual customer relationships
Amortization of intangible assets estimated useful lives
Amortization of intangible assets estimated useful lives	5 years
Minimum | Laboratory | Non-contractual customer relationships
Amortization of intangible assets estimated useful lives
Amortization of intangible assets estimated useful lives	10 years
Maximum | Covenants not-to-compete
Amortization of intangible assets estimated useful lives
Amortization of intangible assets estimated useful lives	25 years
Maximum | Favorable lease assets
Amortization of intangible assets estimated useful lives
Amortization of intangible assets estimated useful lives	27 years
Maximum | Technology
Amortization of intangible assets estimated useful lives
Amortization of intangible assets estimated useful lives	10 years
Maximum | Trademarks
Amortization of intangible assets estimated useful lives
Amortization of intangible assets estimated useful lives	10 years
Maximum | Animal Hospital | Non-contractual customer relationships
Amortization of intangible assets estimated useful lives
Amortization of intangible assets estimated useful lives	7 years
Maximum | Laboratory | Non-contractual customer relationships
Amortization of intangible assets estimated useful lives
Amortization of intangible assets estimated useful lives	25 years