Fair Value Measurements and Financial Instruments - Financial Instruments not Carried at Fair Value (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Kronos Worldwide, Inc. | Revolving North American credit facility
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	$ 18.5
Long term debt, fair value	18.5
Kronos Worldwide, Inc. | Term Loan | 2014 Term Loan
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	336.4	$ 338.0
Long term debt, fair value	331.0	309.5
VALHI, INC. | Contran Credit Facility
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	288.3	263.8
Long term debt, fair value	288.3	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
WCS | Fixed Rate Loans
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	64.4	65.6
Long term debt, fair value	64.4	65.6
Tremont | Promissory Note
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	17.1	17.1
Long term debt, fair value	17.1	17.1
BMI | Bank note payable
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	8.6	9.3
Long term debt, fair value	8.7	9.4
LandWell | Unsecured Debt
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long term debt, carrying amount	3.1	3.1
Long term debt, fair value	3.1	3.1
Reported Value Measurement
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, cash equivalents and restricted cash equivalents	235.2	229.1
Deferred payment obligation	9.0	8.8
Portion at Fair Value Measurement
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, cash equivalents and restricted cash equivalents	235.2	229.1
Deferred payment obligation	$ 9.0	$ 8.8