Summary of significant accounting policies - Research and development incentives and receivable (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Research and development incentives and receivable
Reduction of research and development	$ 23.5	$ 19.3	$ 10.8
Certain research and development expenditures incurred prior to April 1, 2023
Research and development incentives and receivable
Percentage of surrenderable losses	14.50%
Certain research and development expenditures incurred thereafter April 1, 2023
Research and development incentives and receivable
Percentage of surrenderable losses	10.00%