Long-Term Debt - Valhi Contran Credit Facility - Additional Information (Detail)	12 Months Ended
Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
Borrowings of credit facility	$ 0
Repaid credit facility	42,300,000
VALHI, INC. \| Contran Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 320,000,000
Debt instrument, Interest rate at period end	4.25%
Debt due date, start date	Dec. 31, 2022
Amount available for borrowing	$ 49,300,000
Debt instrument basis spread on variable rate	1.00%
Debt instrument, Interest rate during period	4.50%

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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The average effective interest rate during the reporting period.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Earliest date the outstanding debt instruments are required to be repaid, in CCYY-MM-DD format.

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The effective interest rate at the end of the reporting period.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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The cash inflow from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with maturities due beyond one year or the operating cycle, if longer.

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The cash outflow for the settlement of obligation drawn from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with maturities due beyond one year or the operating cycle, if longer.

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