Accounts payable and accrued liabilities - Schedule of Accounts Payable and Accrued Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Accounts payable:
Accounts payable	$ 218.8	$ 250.0
Current accrued liabilities:
Employee benefits	28.1	28.2
Accrued development costs	25.5	30.0
Accrued litigation settlement	16.5	16.4
Deferred income	32.3	38.7
Accrued sales discounts and rebates	10.2	27.6
Interest	2.2	11.4
Operating lease liabilities	$ 3.8	$ 3.5
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Total	Total
Other	$ 58.3	$ 59.7
Total	416.4	482.6
Kronos Worldwide
Accounts payable:
Accounts payable	205.2	232.4
CompX
Accounts payable:
Accounts payable	3.9	3.7
BMI/LandWell
Accounts payable:
Accounts payable	6.8	8.0
Other
Accounts payable:
Distributions payable to noncontrolling interest	2.9	5.9
Contran
Accounts payable:
Contran - other	2.4	0.2
Contran | Income Taxes Payable
Accounts payable:
Income taxes payable current	$ 18.3	$ 16.9