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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (b)
-Publisher FASB
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Fair value measurements and financial instruments - Additional Information (Details) $ in Millions	Mar. 31, 2026 USD ($)	Mar. 31, 2026 EUR (€)	Dec. 31, 2025 USD ($)	Dec. 31, 2025 EUR (€)	Sep. 15, 2025
Fair value measurements and financial instruments
Total debt	$ 625.3		$ 591.7
Kronos Worldwide \| 9.50% Senior Secured Notes due 2029 \| Kronos International, Inc
Fair value measurements and financial instruments
Interest rate	9.50%	9.50%	9.50%	9.50%	9.50%
Estimated market price of the notes \| €		€ 853		€ 937
Principal amount of debt instrument \| €		€ 1,000		€ 1,000
Total debt	$ 490.9		$ 503.7
VALHI, INC. \| Contran Credit Facility
Fair value measurements and financial instruments
Total debt	$ 11.9		$ 23.6