Summary of significant accounting policies - Property and equipment (Details)
12 Months Ended
Dec. 31, 2019
Laboratory equipment  
Property and equipment  
Estimated useful life 5 years
Furniture and office equipment  
Property and equipment  
Estimated useful life 5 years
Computer hardware and software | Minimum  
Property and equipment  
Estimated useful life 3 years
Computer hardware and software | Maximum  
Property and equipment  
Estimated useful life 5 years
Internally developed software | Minimum  
Property and equipment  
Estimated useful life 3 years
Internally developed software | Maximum  
Property and equipment  
Estimated useful life 5 years