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Long-Term Debt - Kronos Term Loans - Additional Information (Detail) - Kronos Worldwide, Inc. - Kronos International, Inc - 3.75% Senior Secured Notes due September 15, 2025		12 Months Ended
	Sep. 13, 2017 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 13, 2017 EUR (€)
Debt Instrument [Line Items]
Debt instrument principal amount	$ 477,600,000			€ 400,000,000
Debt instrument maturity date	Sep. 15, 2025
Debt instrument interest rate	3.75%			3.75%
Debt instrument, interest payment terms		bear interest at 3.75% per annum,
Debt instrument, frequency of periodic payment of interest		semi-annually
Debt Instrument, date of first required semi-annual payment	Mar. 15, 2018
Debt instrument redemption price percent if experiences certain specified change of control events	101.00%
Debt instrument, redemption, description		have a maturity date of September 15, 2025. Prior to September 15, 2020, Kronos had an option to redeem some or all of the Senior Notes at a price equal to 100% of the principal amount thereof, plus a “make-whole” premium (as defined in the indenture governing the Senior Notes). On or after September 15, 2020, Kronos may redeem the Senior Notes at redemption prices ranging from 102.813% of the principal amount, declining to 100% on or after September 15, 2023. In addition, on or before September 15, 2020, Kronos had an option to redeem up to 40% of the Senior Notes with the net proceeds of certain public or private equity offerings at 103.75% of the principal amount but Kronos did not elect this option. If Kronos experiences certain specified change of control events, it would be required to make an offer to purchase the Senior Notes at 101% of the principal amount. Kronos would also be required to make an offer to purchase a specified portion of the Senior Notes at par value in the event that it generates a certain amount of net proceeds from the sale of assets outside the ordinary course of business, and such net proceeds are not otherwise used for specified purposes within a specified time period
Maximum amount of other indebtedness default before triggering customary default provisions	$ 50,000,000.0
Unamortized debt issuance costs		$ 4,700,000	$ 5,300,000
Collateral Pledged \| Direct Domestic Subsidiary of KII and Guarantors
Debt Instrument [Line Items]
Parent company ownership interest	100.00%			100.00%
Collateral Pledged \| Foreign Subsidiary Directly Owned by KII or any Guarantor
Debt Instrument [Line Items]
Parent company ownership interest	65.00%			65.00%
Non-voting Common Stock \| Collateral Pledged \| Foreign Subsidiary Directly Owned by KII or any Guarantor
Debt Instrument [Line Items]
Parent company ownership interest	100.00%			100.00%
Prior to September 15, 2020
Debt Instrument [Line Items]
Debt instrument, redemption price percentage	100.00%
On or After September 15, 2020
Debt Instrument [Line Items]
Debt instrument, redemption price percentage	102.813%
On or After September 15, 2023
Debt Instrument [Line Items]
Debt instrument, redemption price percentage	100.00%
On or Before September 15, 2020
Debt Instrument [Line Items]
Debt instrument, redemption price percentage	103.75%
On or Before September 15, 2020 \| Maximum
Debt Instrument [Line Items]
Debt instrument, percentage of debt that may be redeemed	40.00%