Marketable Securities - Classification of Marketable Securities (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2022	Dec. 31, 2021
Marketable Securities [Line Items]
Market value	$ 3.6	$ 4.2
Cost basis		3.3
Unrealized gain		0.9
Level 1 \| Common stock \| Valhi
Marketable Securities [Line Items]
Market value	3.6	4.1
Cost basis	3.2	3.2
Unrealized gain	$ 0.4	0.9
Level 1 \| Common stock \| NL And CompX
Marketable Securities [Line Items]
Market value		0.1
Cost basis		$ 0.1

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.

No definition available.

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- Definition

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.

+ References

No definition available.

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- Definition

Amount of investment in marketable security, classified as noncurrent.

+ References

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- Definition

Amount of unrealized gain (loss) on investment in marketable security.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(7)(c))
-URI https://asc.fasb.org/extlink&oid=126953954&loc=SL114868664-224227

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