Organization and operations (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended		6 Months Ended
	Aug. 08, 2019	Jun. 05, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Aug. 01, 2019	Jul. 01, 2019	Mar. 19, 2019
Initial Public Offering
Common stock, authorized shares			120,000,000		120,000,000		120,000,000
Common stock, par value			$ 0.001		$ 0.001		$ 0.001
Common stock, aggregate offering price			$ 28		$ 28		$ 28
Proceeds from sale of common stock, net of issuance costs						$ 48,019
Accumulated deficit			(240,156)		(240,156)		(216,244)
Net loss			(12,302)	$ (10,563)	(23,912)	(19,968)
Unrestricted cash and cash equivalents			88,806	$ 72,025	88,806	$ 72,025	$ 109,155
Underwritten public offering
Initial Public Offering
Shares issued under offerings (in shares)	2,700,000
Common stock, par value	$ 0.001
Gross Proceeds From Issuance Of Common Stock	$ 69,000
Stock issuance cost	4,500
Proceeds from sale of common stock, net of issuance costs	$ 64,500
At-the-market offering
Initial Public Offering
Shares issued under offerings (in shares)		2,200,000
Shares issued price (in dollars per share)		$ 22.73
Common stock, par value										$ 0.001
Gross Proceeds From Issuance Of Common Stock		$ 49,700
Stock issuance cost		1,700
Proceeds from sale of common stock, net of issuance costs		$ 48,000
At-the-market offering | Maximum
Initial Public Offering
Common stock, aggregate offering price										$ 50,000
UmanDiagnostics AB Acquisition
Initial Public Offering
Capital stock shares outstanding, percent								95.00%	5.00%
Net loss					$ 600
UmanDiagnostics AB Acquisition | Maximum
Initial Public Offering
Net loss			$ 100