Fair value of financial instruments - Derivative liability (Details) - Recurring basis - Level 3 $ in Thousands	Mar. 31, 2020 USD ($) Y item	Dec. 31, 2019 USD ($) Y item
Encina
Methodologies and significant inputs used in the determination of the fair value
Valuation Method	us-gaap:ValuationTechniqueDiscountedCashFlowMember	us-gaap:ValuationTechniqueDiscountedCashFlowMember
Fair value of liability at valuation date | $	$ 62	$ 66
Encina | Time period from valuation until end of earnout (in years)
Methodologies and significant inputs used in the determination of the fair value
Derivative Liability | Y	2.100	2.400
Encina | Cumulative probability of a change in control prepayment implied by model (in percent)
Methodologies and significant inputs used in the determination of the fair value
Derivative Liability	23.1	23.9
Encina | Discount rate (in percent)
Methodologies and significant inputs used in the determination of the fair value
Derivative Liability	6.50	6.0
Deerfield
Methodologies and significant inputs used in the determination of the fair value
Valuation Method	us-gaap:ValuationTechniqueOptionPricingModelMember	us-gaap:ValuationTechniqueOptionPricingModelMember
Fair value of liability at valuation date | $	$ 1,169	$ 1,069
Deerfield | Time period from valuation until end of earnout (in years)
Methodologies and significant inputs used in the determination of the fair value
Derivative Liability | Y	2.1	2.4
Deerfield | Cumulative probability of a change in control prepayment implied by model (in percent)
Methodologies and significant inputs used in the determination of the fair value
Derivative Liability	22	23
Deerfield | Cumulative probability of other accelerated prepayments implied by model (in percent)
Methodologies and significant inputs used in the determination of the fair value
Derivative Liability	9	10
Deerfield | Discount rate (in percent)
Methodologies and significant inputs used in the determination of the fair value
Derivative Liability	32.47	25.34