Long-Term Debt - Long-Term Debt (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Long-term debt
Total debt	$ 1,043.1	$ 893.8
Less current maturities	1.6	4.5
Total long-term debt	1,041.5	889.3
VALHI, INC.
Long-term debt
Total debt	534.3	528.9
VALHI, INC. | Contran Credit Facility
Long-term debt
Total debt	284.3	278.9
VALHI, INC. | Notes Payable, Other Payables | Snake River
Long-term debt
Total debt	250.0	250.0
Kronos Worldwide, Inc. | 3.75% Senior Secured Notes due September 15, 2025 | Kronos International, Inc
Long-term debt
Total debt	471.1
Kronos Worldwide, Inc. | 2014 Term Loan
Long-term debt
Total debt		335.9
Tremont | Promissory Note
Long-term debt
Total debt	13.1	14.5
BMI | 2018 Notes Payable to Banks | Western Alliance Bank
Long-term debt
Total debt	18.8
BMI | Refinanced Notes Payable to Banks | Meadows Bank
Long-term debt
Total debt		8.4
LandWell | Unsecured Debt
Long-term debt
Total debt	2.5	2.9
Other Subsidiary | Other
Long-term debt
Total debt	3.3	3.2
Subsidiary
Long-term debt
Total debt	$ 508.8	$ 364.9