Long-Term Debt - Long-Term Debt (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Long-term debt
Total long-term debt	$ 653.0	$ 788.6
Less current maturities	(3.1)	(2.4)
Total long-term debt	649.9	786.2
VALHI, INC. | Contran Credit Facility
Long-term debt
Total long-term debt	172.9	270.7
Kronos Worldwide, Inc. | 3.75% Senior Secured Notes due September 15, 2025 | Kronos International, Inc
Long-term debt
Total long-term debt	448.8	485.7
BMI | Bank loan | Western Alliance Bank
Long-term debt
Total long-term debt	15.4	16.3
LandWell | Unsecured Debt. | Western Alliance Bank
Long-term debt
Total long-term debt	13.5	14.2
Others | Other Debt
Long-term debt
Total long-term debt	2.4	1.7
Subsidiary
Long-term debt
Total long-term debt	$ 480.1	$ 517.9