Other noncurrent liabilities - Other noncurrent liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Other noncurrent liabilities
Accrued development costs	$ 41.9	$ 42.3
Operating lease liabilities	$ 17.9	$ 18.6
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Total	Total
Accrued litigation settlement	$ 16.2	$ 16.1
Deferred income	15.2	15.5
Insurance claims and expenses	15.0	14.9
Other postretirement benefits	7.2	7.4
Employee benefits	4.7	4.9
Other	7.8	7.8
Total	$ 125.9	$ 127.5