Marketable securities - Additional Information (Detail) - Valhi Inc - Common stock - $ / shares shares in Millions	Sep. 30, 2024	Dec. 31, 2023
Marketable Securities [Line Items]
Number of shares owned	1.2	1.2
Quoted marked price per share	$ 33.37	$ 15.19

Number of shares of investment owned.

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Name:	us-gaap_InvestmentOwnedBalanceShares
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant