Long-term debt - Components of Long-Term Debt (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Long-term debt
Kronos International, Inc. 3.75% Senior Secured Notes due 2025	$ 440.9	$ 424.1
Other		1.1
Total debt	440.9	425.2
Less current maturities		1.1
Total long-term debt	440.9	424.1
Kronos International, Inc
Long-term debt
Kronos International, Inc. 3.75% Senior Secured Notes due 2025	440.9	424.1
Kronos International, Inc | 3.75% Senior Notes
Long-term debt
Kronos International, Inc. 3.75% Senior Secured Notes due 2025	$ 440.9	$ 424.1