The company and basis of presentation - Liquidity and going concern (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
The company and basis of presentation
Cash and cash equivalents	$ 11,691		$ 17,006
Accumulated deficit	(61,254)		$ (52,280)
Cash used from operations	$ (4,404)	$ (957)