| Intangible assets, net - Tabular Disclosure (Details) - USD ($) $ in Thousands | Sep. 30, 2017 | Dec. 31, 2016 | 
|---|---|---|
| Intangible assets, net | ||
| Acquired software licenses | $ 1,897 | $ 1,493 | 
| Less accumulated amortization | (523) | (225) | 
| Intangible assets, net | 1,374 | 1,268 | 
| Acquired software licenses | ||
| Intangible assets, net | ||
| Acquired software licenses | 1,699 | 1,310 | 
| Licensed IP rights - completed technology used in R&D | ||
| Intangible assets, net | ||
| Acquired software licenses | $ 198 | $ 183 | 
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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://www.xbrl.org/2003/role/presentationRef 
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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/presentationRef 
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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://www.xbrl.org/2003/role/presentationRef 
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- References No definition available. 
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