Marketable securities - Additional Information (Detail) - Valhi Inc - Common stock - $ / shares	Mar. 31, 2026	Dec. 31, 2025
Marketable securities
Investments in publicly-traded shares (in shares)	144,000	144,000
Quoted market price of per share (in dollars per share)	$ 14.3	$ 12.05

Number of shares of investment owned.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/exampleRef
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Name:	us-gaap_InvestmentOwnedBalanceShares
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant