Income Taxes - Components of Net Deferred Tax Liability (Detail) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Components of Deferred Tax Assets and Liabilities [Abstract]
Accrued environmental liabilities	$ 2,831	$ 14,406
Other accrued liabilities and deductible differences	2,138	1,981
Tax loss carryforwards	825
Adjusted gross deferred tax assets (liabilities)	5,794	16,387
Netting of items by tax jurisdiction	(5,794)	(16,387)
Marketable securities	(2,799)	(5,652)
Goodwill	(1,693)	(1,693)
Other taxable differences	(2,945)	(5,733)
Investment in Kronos Worldwide, Inc.	(52,460)	(56,700)
Adjusted gross deferred tax assets (liabilities)	(59,897)	(69,778)
Netting of items by tax jurisdiction	5,794	16,387
Net noncurrent deferred tax liability	$ (54,103)	$ (53,391)