Marketable securities - Schedule of Marketable Securities (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2023	Dec. 31, 2022
Schedule Of Available For Sale Securities [Line Items]
Market value, Current assets	$ 95,688	$ 70,164
Market value, Noncurrent assets	20,852	26,350
Level 1 \| Valhi Inc \| Common stock
Schedule Of Available For Sale Securities [Line Items]
Market value, Noncurrent assets	20,852	26,350
Cost or amortized cost, Noncurrent assets	24,347	24,347
Unrealized Gain (Loss) on Noncurrent Marketable Securities	(3,495)	2,003
Level 2 \| Fixed income securities
Schedule Of Available For Sale Securities [Line Items]
Market value, Current assets	95,688	70,164
Cost or amortized cost, Current assets	95,830	70,226
Unrealized gain (loss), Current assets	$ (142)	$ (62)

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

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

+ References

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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), classified as current.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

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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.

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Amount of investment in marketable security, classified as noncurrent.

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