Fair Value Measurements and Financial Instruments - Financial Instruments not Carried at Fair Value (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Kronos Worldwide, Inc. | 3.75% Senior Secured Notes due September 15, 2025 | Kronos International, Inc
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	$ 464.2
Long term debt, fair value	480.4
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
Long term debt, fair value		334.6
VALHI, INC. | Contran Credit Facility
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	284.3	278.9
Long term debt, fair value	284.3	278.9
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	14.5
Long term debt, fair value	14.5	14.5
BMI | Bank note payable | Meadows Term Loan
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount		8.4
Long term debt, fair value		8.5
BMI | Loan Agreement | Western Alliance Bank
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	18.7
Long term debt, fair value	19.7
LandWell | Unsecured Debt
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	2.7	2.9
Long term debt, fair value	2.7	2.9
Financing capital lease | Waste Control Specialists | Financing Capital Lease Obligation | Andrews County capital lease
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	62.7	64.0
Long term debt, fair value	62.7	64.0
Reported Value Measurement
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, cash equivalents and restricted cash equivalents	475.3	196.5
Deferred payment obligation	9.2	9.0
Estimate of Fair Value Measurement
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, cash equivalents and restricted cash equivalents	475.3	196.5
Deferred payment obligation	$ 9.2	$ 9.0