Other noncurrent assets - Components (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Other assets:
Note receivables - OPA	$ 102.8	$ 91.6
Pension asset	21.9	19.8
Operating lease right-of-use assets	21.5	20.6
IBNR receivables	15.1	15.0
Restricted cash and cash equivalents	6.0	5.5
Land held for development	5.9	7.4
Other	16.8	21.4
Total	$ 190.0	$ 181.3