Commitments and contingencies - Lead Pigment Litigation-NL and Environmental Matters and Litigation - Additional Information (Details)	1 Months Ended	3 Months Ended
	Feb. 28, 2025 USD ($) company	Mar. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)	Jun. 30, 2025 USD ($) site
Commitments and contingencies
Litigation settlement			$ 16,400,000	$ 16,600,000
Accrual for reasonably estimable environmental remediation and related matters			74,600,000	18,600,000
Other Environmental Cleanup Matters
Commitments and contingencies
Accrual for reasonably estimable environmental remediation and related matters				5,000,000
Raritan Bay Slag Superfund Site
Commitments and contingencies
Settlement amount	$ 151,100,000
Number of private companies to pay to resolve all federal and state law claims | company	22
NL Industries
Commitments and contingencies
Settlement interest		$ 500,000
Litigation payment		56,100,000
Litigation settlement, current		$ 9,600,000
Aggregate income			$ 31,400,000
NL Industries | Environmental Remediation Sites NL Named As PRP Or Defendant
Commitments and contingencies
Accrual for reasonably estimable environmental remediation and related matters				$ 13,000,000
Number of sites associated with remediation and related costs				29
Number of sites for which NL not currently able to reasonably estimate range of costs | site				5
NL Industries | Maximum | Environmental Remediation Sites NL Named As PRP Or Defendant
Commitments and contingencies
Upper end range, estimate costs for remediation and related matters				$ 38,000,000
C A Lead Paint Litigation | NL Industries
Commitments and contingencies
Remaining litigation settlement charge due in sixth installment				$ 16,700,000