Fair value measurement - Valuation technique and inputs used in determining the fair value of contingent consideration (Details)	Mar. 31, 2019
Milestone-based payment | Minimum | Discounted cash flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Business combination, contingent consideration, liability, measurement input	0.041
Milestone-based payment | Maximum | Discounted cash flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Business combination, contingent consideration, liability, measurement input	0.057
Revenue-based | Minimum | 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 | Minimum | Monte Carlo simulation | Revenue volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Business combination, contingent consideration, liability, measurement input	0.197
Revenue-based | Maximum | Discounted cash flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Business combination, contingent consideration, liability, measurement input	0.105
Revenue-based | Maximum | Monte Carlo simulation | Revenue volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Business combination, contingent consideration, liability, measurement input	0.247