Long-Term Debt - Valhi - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018
Contran Credit Facility
Debt Instrument [Line Items]
Amount available for borrowing	$ 39,400,000
Contran Credit Facility | Waste Management | Subsequent Event
Debt Instrument [Line Items]
Noncash borrowings		$ 36,300,000
VALHI, INC. | Contran Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 360,000,000
Debt instrument, Interest rate at period end	5.50%
Debt due date, start date	Dec. 31, 2019
Credit facility, Amount borrowed	$ 5,400,000
Amount available for borrowing	$ 75,700,000
Debt instrument basis spread on variable rate	1.00%
Debt instrument, average interest rate during period	5.10%
VALHI, INC. | Notes Payable, Other Payables | Snake River
Debt Instrument [Line Items]
Term loan	$ 250,000,000
Loans bear interest at a weighted average fixed interest rate	9.40%
Debt instrument maturity date	Jan. 31, 2027
Recourse loans	$ 37,500,000
Nonrecourse loans	$ 212,500,000
WCS | Subsequent Event | Contran | Amounts Acquired in Business Divestiture
Debt Instrument [Line Items]
Acquired trade receivable		$ 36,300,000