Income taxes - Components of income (loss) before income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Components of income (loss) before income taxes
United States	$ (40,010)	$ (31,436)	$ (27,019)
Foreign	(973)	(75)
Loss before income tax	$ (40,983)	$ (31,511)	$ (27,019)

The portion of earnings or loss from continuing operations before income taxes that is attributable to domestic operations.

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Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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The portion of earnings or loss from continuing operations before income taxes that is attributable to foreign operations, which is defined as Income or Loss generated from operations located outside the entity's country of domicile.

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