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Organization and basis of presentation - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2025 USD ($) a	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Jul. 16, 2024	Jul. 15, 2024
Organization and basis of presentation
Cost of sales	$ 1,781.6	$ 1,680.3	$ 1,676.5
Capitalized interest costs on property and equipment	$ 1.8	1.0	1.9
Percentage of likelihood for recognition of uncertain tax positions	50.00%
Standard payment terms	less than one year
Advertising costs	$ 2.0	2.0	2.0
Research, development and certain sales technical support costs	17.0	14.0	18.0
Louisiana Pigment Company, L.P. (LPC)
Organization and basis of presentation
Percentage owned manufacturing joint venture under equity method investment					50.00%
Chemicals
Organization and basis of presentation
Cost of sales	1,648.4	1,530.1	1,502.7
Shipping and Handling \| Chemicals
Organization and basis of presentation
Cost of sales	$ 126.0	115.0	101.0
Residential or planned community
Organization and basis of presentation
Area of real estate property \| a	2,100
Residential Housing Unit \| Minimum
Organization and basis of presentation
Percentage of sales price	2.50%
Residential Housing Unit \| Maximum
Organization and basis of presentation
Percentage of sales price	3.50%
Kronos \| Louisiana Pigment Company, L.P. (LPC)
Organization and basis of presentation
Percentage held through wholly-owned subsidiary				50.00%
Percentage acquired				50.00%
Contran
Organization and basis of presentation
Net cash payments received from/paid to tax group parent	$ 18.5	$ 19.1	$ 14.2
Contran \| Valhi Incorporation
Organization and basis of presentation
Parent company ownership interest	91.00%