Acquisitions (Details) $ in Thousands, € in Millions	3 Months Ended			6 Months Ended	12 Months Ended
	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($) entity	Mar. 31, 2017 EUR (€)	Dec. 31, 2017 USD ($) item	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) entity
Business Acquisition [Line Items]
Acquisition of a business, net of cash acquired					$ 14,579	$ 1,964	$ 10,302
Business Combinations, goodwill					13,541	1,720	$ 5,047
Two Software Companies [Member]
Business Acquisition [Line Items]
Number of businesses acquired | entity		2
Business Combination, Consideration Transferred		$ 15,000
Acquisition of a business, net of cash acquired		12,000
Contingent payment		$ 3,000
Business Combination Contingent Consideration Term For Payment Upon Completion Of Goals		36 months
Business Combinations, goodwill	$ 13,300
Reference Laboratory In Austria [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred | €			€ 1.3
Reference Laboratory Diagnostic And Consulting Businesses [Member]
Business Acquisition [Line Items]
Number of businesses acquired | entity							2
Acquisition of a business, net of cash acquired						$ 3,500
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
Customer Lists [Member] | Reference Laboratory In United States [Member]
Business Acquisition [Line Items]
Number of businesses acquired | item				4
Business Combination, Consideration Transferred				$ 2,300
Contingent payment				$ 400	$ 400
Customer Lists [Member] | Reference Laboratory Diagnostic And Consulting Businesses [Member]
Business Acquisition [Line Items]
Useful life assigned to intangible asset, years							15 years
Intangibles acquired as result of business combination							$ 5,200
Customer Relationships [Member] | Two Software Companies [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	1,000
Technology-Based Intangible Assets [Member] | Two Software Companies [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	$ 600