Accounts payable and accrued liabilities - Schedule of Accounts Payable and Accrued Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Accounts payable:
Accounts payable	$ 195.2	$ 250.0
Current accrued liabilities:
Employee benefits	35.1	38.7
Deferred income	27.4	28.2
Accrued development costs	22.4	30.0
Accrued sales discounts and rebates	17.0	27.6
Accrued litigation settlement	16.6	16.4
Interest	12.5	11.4
Operating lease liabilities	$ 4.2	$ 3.5
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Total	Total
Other	$ 49.0	$ 59.7
Total	380.7	482.6
Kronos Worldwide
Accounts payable:
Accounts payable	187.0	232.4
CompX
Accounts payable:
Accounts payable	4.1	3.7
BMI/LandWell
Accounts payable:
Accounts payable	3.1	8.0
Other
Accounts payable:
Distributions payable to noncontrolling interest	1.0	5.9
Contran | Income Taxes Payable
Accounts payable:
Income taxes payable current		16.9
Contran | Other payables
Current accrued liabilities:
Payables to affiliates	$ 1.3	$ 0.2