Summary of Significant Accounting Policies - Narrative (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) segment	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Allowance for credit losses	$ 100,000		$ 100,000		$ 0
Number of operating segments | segment			1
Impairment of goodwill	0		$ 0
Revenue from cash collections exceeding estimated variable consideration	6,500,000	$ 3,600,000	12,400,000	$ 6,400,000
Change in estimate of development services revenue				3,600,000
Unbilled receivables	9,500,000		9,500,000		6,200,000
Deferred revenue	11,500,000		11,500,000		12,300,000
Deferred revenue recognized			7,600,000
Medicare
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue from samples processed in the previous year	2,600,000	$ 1,400,000	4,100,000	$ 1,400,000
Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue	6,400,000		6,400,000		4,800,000
Other Assets
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Unbilled receivables	$ 200,000		$ 200,000		$ 1,000,000.0
Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Useful life (years)			6 years
Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Useful life (years)			12 years