Business combinations - Clear Genetics (Details) - USD ($) $ in Thousands, shares in Millions	1 Months Ended		3 Months Ended	9 Months Ended
	Apr. 30, 2020	Nov. 30, 2019	Jun. 30, 2020	Sep. 30, 2020
Business Acquisition [Line Items]
Business combination, total purchase consideration	$ 65,913
Hold-back consideration - cash	1,385
Hold-back consideration - common stock	$ 6,173
Clear Genetics
Business Acquisition [Line Items]
Percentage of diluted interest acquired		100.00%
Business combination, total purchase consideration		$ 50,100
Common stock issued pursuant to business combinations (in shares)			0.1
Hold-back consideration - common stock				$ 12,200
Indemnification obligations | Clear Genetics
Business Acquisition [Line Items]
Hold-back consideration - cash		$ 200
Business acquisition common stock issued (in shares)		0.4		0.3