Organization and operations (Details) $ / shares in Units, $ in Thousands				1 Months Ended	3 Months Ended								12 Months Ended
	Aug. 08, 2019 USD ($) $ / shares shares	Jun. 05, 2019 USD ($) $ / shares shares	Dec. 04, 2017	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) $ / shares shares	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Aug. 01, 2019	Jul. 01, 2019	Mar. 19, 2019 USD ($) $ / shares	Jan. 01, 2019 USD ($)
Initial Public Offering
Shares issued | shares	2,700,000
Common stock, authorized shares | shares					120,000,000				120,000,000				120,000,000	120,000,000
Preferred stock authorized (in shares) | shares					47,015,449								47,015,449
Share value | $ / shares					$ 0.001				$ 0.001				$ 0.001	$ 0.001
Common stock, aggregate offering price					$ 28				$ 22				$ 28	$ 22
stock issuance cost															$ 8,173
Net proceeds from issuance of common shares														(20)	8,423
Accumulated deficit					(216,244)				(175,888)				(216,244)	(175,888)					$ (175,448)
Net loss					(10,958)	$ (9,870)	$ (10,563)	$ (9,405)	(9,334)	$ (7,657)	$ (7,343)	$ (7,202)	(40,796)	(31,536)	(27,019)
Unrestricted cash and cash equivalents				$ 79,682	$ 109,155				$ 44,429				109,155	$ 44,429	$ 79,682
Common stock
Initial Public Offering
Conversion of preferred stock to common stock (in shares) | shares															14,185,744
Reverse stock split ratio			0.311
Initial Public Offering
Initial Public Offering
Shares issued | shares				4,916,480
Shares issued price (in dollars per share) | $ / shares				$ 15.00											$ 15.00
Aggregate net proceeds from IPO				$ 65,600
Conversion of preferred stock to common stock (in shares) | shares				14,185,744
Carrying value of preferred stock, notes and warrants reclassified as common stock and additional paid-in capital				$ 143,300											$ 143,300
Common stock, authorized shares | shares				120,000,000											120,000,000
Preferred stock authorized (in shares) | shares				5,000,000											5,000,000
Initial Public Offering | Common stock
Initial Public Offering
Shares issued | shares															4,916,480
Underwritten public offering
Initial Public Offering
Shares issued | shares	2,700,000
Share value | $ / shares	$ 0.001
Gross Proceeds From Issuance Of Common Stock	$ 69,000
stock issuance cost	4,500
Net proceeds from issuance of common shares	$ 64,500												$ 64,529
Underwritten public offering | Common stock
Initial Public Offering
Shares issued | shares													2,732,673
At-the-market offering
Initial Public Offering
Shares issued | shares		2,200,000
Shares issued price (in dollars per share) | $ / shares		$ 22.73
Share value | $ / shares																		$ 0.001
Gross Proceeds From Issuance Of Common Stock		$ 49,700
stock issuance cost		1,700
Net proceeds from issuance of common shares		$ 48,000											$ 48,019
At-the-market offering | Maximum
Initial Public Offering
Common stock, aggregate offering price																		$ 50,000
At-the-market offering | Common stock
Initial Public Offering
Shares issued | shares													2,186,163
UmanDiagnostics AB Acquisition
Initial Public Offering
Capital stock shares outstanding, percent																95.00%	5.00%
Net loss													$ 100