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Share-based awards - Schedule of Weighted Average Fair Values and Assumptions Used (Details) - Employee Stock Option - $ / shares
9 Months Ended
Sep. 30, 2021
Jul. 01, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Weighted average grant date fair value   $ 107.21   $ 49.15 $ 42.43
Assumptions:          
Expected volatility   30.00%   30.00% 30.00%
Dividend yield   0.00%   0.00% 0.00%
Risk-free interest rate   0.56%   0.78% 0.57%
Expected life 5 years 3 years 6 months 5 years