| Intangible assets, net - Tabular Disclosure (Details) - USD ($) $ in Thousands | Jun. 30, 2016 | Dec. 31, 2015 | 
|---|---|---|
| Intangible assets, net | ||
| Acquired software licenses | $ 1,173 | $ 399 | 
| Less accumulated amortization | (163) | (94) | 
| Intangible assets, net | 1,010 | 305 | 
| Acquired software licenses | ||
| Intangible assets, net | ||
| Acquired software licenses | 1,080 | $ 399 | 
| IP rights for licensed technology | ||
| Intangible assets, net | ||
| Acquired software licenses | $ 93 | 
| X | ||||||||||
| 
- 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 
 | 
| X | ||||||||||
| 
- 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 
 | 
| X | ||||||||||
| 
- 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 
 | 
| X | ||||||||||
| 
- References No definition available. 
 | 
| X | ||||||||||
| 
- Details 
 | 
| X | ||||||||||
| 
- Details 
 |