Marketable securities - Schedule of Marketable Securities (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2024	Dec. 31, 2023
Marketable Securities [Line Items]
Market value, Current assets	$ 11,934	$ 53,149
Market value, Noncurrent assets	21,356	18,194
Level 1 \| Valhi Inc \| Common stock
Marketable Securities [Line Items]
Market value, Noncurrent assets	21,356	18,194
Cost or amortized cost, Noncurrent assets	24,347	24,347
Unrealized gain (loss), Noncurrent assets	(2,991)	(6,153)
Level 2 \| Fixed income securities
Marketable Securities [Line Items]
Market value, Current assets	11,934	53,149
Cost or amortized cost, Current Assets	11,935	53,181
Unrealized gain (loss), Current assets	$ (1)	$ (32)

Amount of unrealized gain (loss) on current marketable securities.

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Amount of unrealized gain (loss) on non current marketable securities.

+ References

No definition available.

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- Definition

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479130/326-30-45-1

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Cost of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value.

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Amount of investment in marketable security, classified as current.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of investment in marketable security, classified as noncurrent.

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