Acquisitions - Narrative (Details) - USD ($)					1 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Jun. 18, 2021	Apr. 07, 2021	Jan. 01, 2020	Apr. 30, 2021	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Mar. 31, 2021	Dec. 31, 2020	May 31, 2020	May 22, 2020
Business Acquisition [Line Items]
Plus: Cash paid at closing							$ 419,404,000	$ 37,000,000
Common stock, par value (in dollars per share)	$ 0.001					$ 0.001	$ 0.001			$ 0.001
Gain on investment in and loan receivable from non-consolidated affiliate, net							$ 109,260,000	$ 0
Goodwill	$ 525,802,000					$ 525,802,000	525,802,000			$ 211,083,000
Clinical Services
Business Acquisition [Line Items]
Goodwill	461,449,000					461,449,000	461,449,000			179,534,000
Pharma Services
Business Acquisition [Line Items]
Goodwill	64,353,000					64,353,000	$ 64,353,000			$ 31,549,000
Inivata Limited
Business Acquisition [Line Items]
Amount outstanding under line of credit		$ 10,300,000
Variable Interest Entity, Not Primary Beneficiary | Inivata Limited
Business Acquisition [Line Items]
Investment in minority interest		29,600,000							$ 29,600,000		$ 25,000,000	$ 25,000,000
Consideration paid to other shareholders		390,000,000
Variable Interest Entity, Not Primary Beneficiary | Inivata Limited | Preference Shares
Business Acquisition [Line Items]
Investment in minority interest		25,000,000							25,000,000			19,600,000
Variable Interest Entity, Not Primary Beneficiary | Inivata Limited | Purchase Option
Business Acquisition [Line Items]
Investment in minority interest		4,600,000							$ 4,600,000			$ 6,000,000
Identifiable intangible assets - developed technology(1) | Minimum
Business Acquisition [Line Items]
Amortization period of acquired intangible assets							10 years
Identifiable intangible assets - developed technology(1) | Maximum
Business Acquisition [Line Items]
Amortization period of acquired intangible assets							15 years
Marketing Assets
Business Acquisition [Line Items]
Amortization period of acquired intangible assets							4 years
Trademarks
Business Acquisition [Line Items]
Amortization period of acquired intangible assets							15 years
Trade Name
Business Acquisition [Line Items]
Amortization period of acquired intangible assets							5 years
Trapelo Health
Business Acquisition [Line Items]
Percentage of voting interests acquired (as a percent)			100.00%
Plus: Cash paid at closing			$ 35,591,000
Payments to acquire business, adjustments			600,000
Common stock issued for consideration			$ 29,174,000
Shares of common stock issued as consideration (in shares)			597,712		597,712
Stock price per share on closing date (in dollars per share)			$ 48.81
Amortization period of acquired intangible assets			9 years 9 months 18 days
Goodwill acquired							$ 44,664,000
Acquisition and integration costs						100,000	1,600,000
Goodwill			$ 44,664,000
Goodwill, tax deductible			$ 0
Trapelo Health | Clinical Services
Business Acquisition [Line Items]
Goodwill acquired							44,664,000
Trapelo Health | Pharma Services
Business Acquisition [Line Items]
Goodwill acquired							0
Trapelo Health | Identifiable intangible assets - developed technology(1)
Business Acquisition [Line Items]
Intangible assets, useful life			10 years
Trapelo Health | Marketing Assets
Business Acquisition [Line Items]
Intangible assets, useful life			4 years
Inivata
Business Acquisition [Line Items]
Plus: Cash paid at closing		398,594,000
Payments to acquire business, adjustments		$ 8,600,000
Amortization period of acquired intangible assets		14 years 10 months 24 days
Goodwill acquired		$ 61,300,000					270,055,000
Acquisition and integration costs				$ 11,700,000		1,500,000
Fair value of previously-held equity interest(1)	64,900,000	64,906,000
Fair value of Purchase Option(1)	$ 74,300,000	74,300,000
Line of credit settled as consideration for acquisition		15,000,000
Gain on investment in and loan receivable from non-consolidated affiliate, net						17,800,000	109,300,000
Measurement period adjustments, net assets acquired		17,750,000				17,800,000
Goodwill		270,055,000
Revenue from acquiree						700,000	700,000
Net loss from acquiree						$ 14,800,000	17,100,000
Acquisition related costs				$ 11,000,000
Goodwill, tax deductible		0
Inivata | Clinical Services
Business Acquisition [Line Items]
Goodwill acquired							237,251,000
Goodwill		237,300,000
Inivata | Pharma Services
Business Acquisition [Line Items]
Goodwill acquired							$ 32,804,000
Goodwill		$ 32,800,000
Inivata | Identifiable intangible assets - developed technology(1) | Maximum
Business Acquisition [Line Items]
Intangible assets, useful life		15 years
Inivata | Trademarks | Maximum
Business Acquisition [Line Items]
Intangible assets, useful life		15 years
Inivata | Trade Name
Business Acquisition [Line Items]
Intangible assets, useful life		5 years