Summary of significant accounting policies - Property and Equipment (Details)	12 Months Ended
Dec. 31, 2019
Computer hardware and software
Property, Plant and Equipment
Useful lives	3 years
Office equipment
Property, Plant and Equipment
Useful lives	5 years
Furniture and fixtures
Property, Plant and Equipment
Useful lives	5 years
Leasehold improvements
Property, Plant and Equipment
Useful lives	3 years

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

No definition available.

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration