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Amount of long-term debt and capital lease obligations including current maturities.

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Long-Term Debt - Valhi Contran Credit Facility - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Aug. 31, 2018	Jan. 26, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Outstanding debt obligations	$ 811.3			$ 1,043.1
Contran Credit Facility
Debt Instrument [Line Items]
Repaid amount	6.3
Contran Credit Facility \| Waste Management
Debt Instrument [Line Items]
Noncash borrowings	36.3		$ 36.3
VALHI, INC.
Debt Instrument [Line Items]
Outstanding debt obligations	314.3			534.3
VALHI, INC. \| Snake River
Debt Instrument [Line Items]
Outstanding debt obligations		$ 250.0
VALHI, INC. \| Contran Credit Facility
Debt Instrument [Line Items]
Outstanding debt obligations	$ 314.3			$ 284.3
Debt instrument, Interest rate at period end	6.25%
Debt instrument, average interest rate during period	5.77%
Amount available for borrowing	$ 45.7
WCS \| Contran Credit Facility \| Contran \| Amounts Acquired in Business Divestiture
Debt Instrument [Line Items]
Acquired trade receivable	$ 36.3		$ 36.3