Fair value measurements and financial instruments- Financial Instruments not Carried at Fair Value (Detail) € in Thousands, $ in Millions	Sep. 30, 2024 EUR (€)	Sep. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)
Reported Value Measurement
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, cash equivalents and restricted cash equivalents		$ 365.1	$ 462.0
Estimate of Fair Value Measurement
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, cash equivalents and restricted cash equivalents		365.1	462.0
Kronos Worldwide, Inc. | Kronos International, Inc
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount		25.0
Long term debt, fair value		25.0
Kronos Worldwide, Inc. | 9.50% Senior Secured Notes due 2029 | Kronos International, Inc
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	€ 351,174	391.7
Long term debt, fair value		427.9
Kronos Worldwide, Inc. | 3.75% Senior Secured Notes due 2025 | Kronos International, Inc
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount		83.9	440.9
Long term debt, fair value		83.3	424.5
LandWell | Bank note payable
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount		11.9	12.2
Long term debt, fair value		$ 11.9	$ 12.2