Other noncurrent liabilities - Other noncurrent liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Other noncurrent liabilities
Accrued development costs	$ 41.4	$ 42.3
Operating lease liabilities	$ 18.1	$ 18.6
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Total	Total
Accrued litigation settlement	$ 16.3	$ 16.1
Insurance claims and expenses	15.0	14.9
Deferred income	12.2	15.5
Other postretirement benefits	7.1	7.4
Employee benefits	4.6	4.9
Other	8.0	7.8
Total	$ 122.7	$ 127.5