Fair value measurement - Valuation technique and inputs used in determining the fair value of contingent consideration (Details)	Jun. 30, 2019
Milestone-based payments | Minimum | Discounted cash flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Business combination, contingent consideration, liability, measurement input	0.037
Milestone-based payments | Maximum | Discounted cash flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Business combination, contingent consideration, liability, measurement input	0.043
Revenue-based payments | Discounted cash flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Business combination, contingent consideration, liability, measurement input	0.100
Revenue-based payments | Minimum | Monte Carlo simulation | Revenue volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Business combination, contingent consideration, liability, measurement input	0.190
Revenue-based payments | Maximum | Monte Carlo simulation | Revenue volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Business combination, contingent consideration, liability, measurement input	0.243