Long-Term Debt - Long-Term Debt (Detail) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Long-term debt
Total debt	$ 641.3	$ 653.0
Less current maturities	(3.1)	(3.1)
Total long-term debt	638.2	649.9
VALHI, INC. | Contran Credit Facility
Long-term debt
Total debt	167.2	172.9
Kronos Worldwide, Inc. | 3.75% Senior Secured Notes due September 15, 2025 | Kronos International, Inc
Long-term debt
Total debt	442.9	448.8
BMI | Bank loan | Western Alliance Bank
Long-term debt
Total debt	15.4	15.4
LandWell | Unsecured Debt | Western Alliance Bank
Long-term debt
Total debt	13.5	13.5
Other Subsidiary | Other
Long-term debt
Total debt	2.3	2.4
Subsidiary
Long-term debt
Total debt	$ 474.1	$ 480.1