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Stock-based compensation - Summary of Weighted-average Assumptions (Details) - Service-based Stock Options
3 Months Ended 12 Months Ended
Mar. 31, 2019
Mar. 31, 2021
Mar. 31, 2020
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expected term (in years) 6 years 3 months 18 days   6 years 6 months 6 years 3 months 18 days
Expected volatility 35.13%   35.57% 32.02%
Risk-free interest rate 2.55%   2.07% 2.68%
Expected dividend yield 0.00% 0.00% 0.00% 0.00%