Contractual interest rate for funds borrowed, under the debt agreement.

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
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

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The cash inflow from the issuance of long-term debt that is not secured by collateral. Excludes proceeds from tax exempt unsecured debt.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
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Financial instrument at fair value.

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Fair value measurements and financial instruments - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($)	Mar. 31, 2025 USD ($)	Mar. 31, 2025 EUR (€)	Dec. 31, 2024 USD ($)	Feb. 12, 2024
Financial instruments
Subordinated, Unsecured Term Loan from Contran \| $	$ 53.7
Valhi - Contran credit facility \| $		$ 607.8		$ 563.4
Kronos Worldwide \| 9.50% Senior Secured Notes due 2029
Financial instruments
Interest rate					9.50%
Kronos Worldwide \| 9.50% Senior Secured Notes due 2029 \| Kronos International, Inc
Financial instruments
Interest rate		9.50%	9.50%	9.50%
Estimated market price of the notes \| €			€ 1,085
Principal amount of debt instrument \| €			€ 1,000
Valhi - Contran credit facility \| $		$ 379.1		$ 365.4
Kronos Worldwide \| 3.75% Senior Secured Notes due 2025 \| Kronos International, Inc
Financial instruments
Interest rate		3.75%	3.75%	3.75%
Estimated market price of the notes \| €			€ 994
Principal amount of debt instrument \| €			€ 1,000
Valhi - Contran credit facility \| $		$ 81.2		$ 78.3