Fair Value Measurements and Financial Instruments - Financial Instruments not Carried at Fair Value (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Valhi stockholders' equity	$ 576,400,000	$ 601,300,000
Carrying Amount
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, cash equivalents and restricted cash equivalents	269,300,000	186,800,000
Deferred payment obligation	8,400,000	8,200,000
Valhi stockholders' equity	576,400,000	601,300,000
Fair Value
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, cash equivalents and restricted cash equivalents	269,300,000	186,800,000
Deferred payment obligation	8,400,000	8,200,000
Valhi stockholders' equity	2,214,500,000	5,916,700,000
Kronos Worldwide, Inc. | Carrying Amount | Non-controlling interest
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Noncontrolling interest	234,700,000	241,900,000
Kronos Worldwide, Inc. | Carrying Amount | Reportable Legal Entities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Loans payable	346,700,000
Kronos Worldwide, Inc. | Carrying Amount | Reportable Legal Entities | Contran
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Notes payable		170,000,000
Kronos Worldwide, Inc. | Carrying Amount | Reportable Legal Entities | Credit Facility
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Credit facility		11,100,000
Kronos Worldwide, Inc. | Fair Value | Non-controlling interest
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Noncontrolling interest	312,300,000	431,600,000
Kronos Worldwide, Inc. | Fair Value | Reportable Legal Entities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Loans payable	343,900,000
Kronos Worldwide, Inc. | Fair Value | Reportable Legal Entities | Contran
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Notes payable		170,000,000
Kronos Worldwide, Inc. | Fair Value | Reportable Legal Entities | Credit Facility
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Credit facility		11,100,000
Snake River | Carrying Amount | Reportable Legal Entities | Fixed Rate Loans
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Loans payable	250,000,000	250,000,000
Snake River | Fair Value | Reportable Legal Entities | Fixed Rate Loans
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Loans payable	250,000,000	250,000,000
WCS | Carrying Amount | Reportable Legal Entities | Unsecured Debt
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Loans payable	69,900,000	72,400,000
WCS | Fair Value | Reportable Legal Entities | Unsecured Debt
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Loans payable	69,900,000	72,400,000
VALHI, INC. | Carrying Amount | Credit Facility | Contran
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Credit facility	221,600,000	206,500,000
VALHI, INC. | Fair Value | Credit Facility | Contran
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Credit facility	221,600,000	206,500,000
Tremont | Carrying Amount | Reportable Legal Entities | Promissory Note
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Notes payable	17,400,000	19,100,000
Tremont | Fair Value | Reportable Legal Entities | Promissory Note
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Notes payable	17,400,000	19,100,000
BMI | Carrying Amount | Reportable Legal Entities | Bank note payable
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Notes payable	10,500,000	11,200,000
BMI | Fair Value | Reportable Legal Entities | Bank note payable
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Notes payable	10,500,000	11,200,000
LandWell | Carrying Amount | Reportable Legal Entities | Unsecured Debt
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Notes payable	3,100,000	3,100,000
LandWell | Fair Value | Reportable Legal Entities | Unsecured Debt
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Notes payable	3,100,000	3,100,000
NL | Carrying Amount | Non-controlling interest
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Noncontrolling interest	58,800,000	74,500,000
NL | Fair Value | Non-controlling interest
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Noncontrolling interest	61,000,000	92,600,000
CompX | Carrying Amount | Non-controlling interest
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Noncontrolling interest	14,300,000	13,600,000
CompX | Fair Value | Non-controlling interest
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Noncontrolling interest	$ 17,000,000	$ 23,100,000