Acquisitions (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) entity	Dec. 31, 2014 USD ($) item
Acquisitions And Strategic Investments [Line Items]
Acquisition of a business, net of cash acquired	$ 1,964	$ 10,302	$ 25,115
Number of businesses acquired | item			7
Business Combinations, goodwill	1,720	$ 5,047	$ 13,077
Business Combination, Consideration Transferred			24,900
Proceeds from sale of equity investment			5,400
Reference Laboratory Diagnostic And Consulting Businesses [Member]
Acquisitions And Strategic Investments [Line Items]
Acquisition of a business, net of cash acquired	$ 3,500
Number of businesses acquired | entity		2
Contingent consideration		$ 3,200
Business Combinations, goodwill		5,000
Cash payments to acquire businesses		7,500
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets		1,100
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment		300
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Noncurrent		$ 900
Cloud-based Veterinary Practice Software Businesses [Member]
Acquisitions And Strategic Investments [Line Items]
Acquisition of a business, net of cash acquired			$ 18,700
Number of businesses acquired | item			3
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill			$ 11,700
Business Combinations, goodwill			$ 12,400
Weighted average useful lives of amortizable intangible assets			11 years 4 months 24 days
Amortizable intangible assets deductible for income tax purposes			$ 5,600
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Contingent Liability			$ 4,200
Assets Of Cloud-based Veterinary Practice Software Businesses [Member]
Acquisitions And Strategic Investments [Line Items]
Number of businesses acquired | item			2
Cloud-based Veterinary Practice Software Businesses, Foreign [Member]
Acquisitions And Strategic Investments [Line Items]
Number of businesses acquired | item			2
Veterinary Reference Laboratory Testing Businesses [Member]
Acquisitions And Strategic Investments [Line Items]
Acquisition of a business, net of cash acquired			$ 6,200
Number of businesses acquired | item			2
Weighted average useful lives of amortizable intangible assets			13 years 3 months 18 days
Amortizable intangible assets deductible for income tax purposes			$ 4,900
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Contingent Liability			$ 1,500
Computer Software, Intangible Asset [Member] | Cloud-based Veterinary Practice Software Businesses [Member]
Acquisitions And Strategic Investments [Line Items]
Weighted average useful lives of amortizable intangible assets			7 years
Customer Lists [Member] | Reference Laboratory Diagnostic And Consulting Businesses [Member]
Acquisitions And Strategic Investments [Line Items]
Useful life assigned to intangible asset, years		15 years
Intangibles acquired as result of business combination		$ 5,200
Customer Lists [Member] | Cloud-based Veterinary Practice Software Businesses [Member]
Acquisitions And Strategic Investments [Line Items]
Weighted average useful lives of amortizable intangible assets			16 years 4 months 24 days