| Intangible assets, net - Tabular Disclosure (Details) - USD ($) $ in Thousands | Dec. 31, 2018 | Dec. 31, 2017 | 
|---|---|---|
| Intangible assets, net | ||
| Intangible assets, gross | $ 2,691 | $ 1,989 | 
| Less accumulated amortization | (1,218) | (652) | 
| Intangible assets, net | 1,473 | 1,337 | 
| Acquired software licenses | ||
| Intangible assets, net | ||
| Intangible assets, gross | 2,494 | 1,789 | 
| Licensed IP rights - completed technology used in R&D | ||
| Intangible assets, net | ||
| Intangible assets, gross | $ 197 | $ 200 | 
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- Definition Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- References No definition available. 
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- Details 
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- Details 
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