Financial Instruments - Financial Instruments not Carried at Fair Value (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Kronos Worldwide, Inc. | Term Loan | 2014 Term Loan
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	$ 335.9	$ 338.0
Long term debt, fair value	334.6	309.5
VALHI, INC. | Contran Credit Facility
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	278.9	263.8
Long term debt, fair value	278.9	263.8
VALHI, INC. | Term Loan | Snake River
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	250.0	250.0
Long term debt, fair value	250.0	250.0
Tremont | Promissory Note
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	14.5	17.1
Long term debt, fair value	14.5	17.1
BMI | Bank note payable
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	8.4	9.3
Long term debt, fair value	8.5	9.4
LandWell | Unsecured Debt
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	2.9	3.1
Long term debt, fair value	2.9	3.1
Reported Value Measurement
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, cash equivalents and restricted cash equivalents	191.0	229.1
Deferred payment obligation	9.0	8.8
Estimate of Fair Value Measurement
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, cash equivalents and restricted cash equivalents	191.0	229.1
Deferred payment obligation	9.0	8.8
Financing capital lease | WCS | Financing Capital Lease Obligation | Andrews County capital lease
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	64.0	65.6
Long term debt, fair value	$ 64.0	$ 65.6