Long-term debt - Kronos 9.50 Senior Secured Notes - Additional Information (Details) $ in Millions				3 Months Ended	12 Months Ended
	Jul. 30, 2024 USD ($)	Feb. 12, 2024 USD ($)	Feb. 12, 2024 EUR (€)	Mar. 31, 2024 USD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2024 EUR (€)	Aug. 31, 2024	Jul. 31, 2024	Jul. 30, 2024 EUR (€)	Jul. 17, 2024 USD ($)	Jul. 16, 2024 USD ($)	Dec. 31, 2023 USD ($)
Debt Instrument [Line Items]
Kronos term loan from Contran					$ 53.7
Kronos Worldwide | Global Revolver Credit Facility
Debt Instrument [Line Items]
Line of credit maximum borrowing capacity	$ 300.0									$ 300.0	$ 225.0
Kronos Worldwide | Kronos International, Inc
Debt Instrument [Line Items]
Long term debt, carrying amount					$ 10.0
Kronos Worldwide | 9.50% Senior Secured Notes due 2029
Debt Instrument [Line Items]
Debt instrument interest rate	9.50%		9.50%						9.50%
Debt instrument principal amount | €			€ 276,174,000						€ 75,000,000
Debt Instrument Exchanged, Principal Amount of Each Instrument | €			850
Debt Instrument Exchanged, Cash Paid For Each Instrument | €			€ 150
Premium percentage	107.50%								107.50%
Net proceeds from issuance	$ 90.0
Debt instrument, redemption price percentage		100.00%	100.00%
Kronos Worldwide | 9.50% Senior Secured Notes due 2029 | On or After March 15, 2026
Debt Instrument [Line Items]
Debt instrument, redemption price percentage		104.75%	104.75%
Kronos Worldwide | 9.50% Senior Secured Notes due 2029 | On or After March 15, 2028
Debt Instrument [Line Items]
Debt instrument, redemption price percentage		100.00%	100.00%
Kronos Worldwide | 9.50% Senior Secured Notes due 2029 | On or Before March 15, 2026
Debt Instrument [Line Items]
Debt instrument, redemption price percentage		109.50%	109.50%
Debt instrument, percentage of debt that may be redeemed		40.00%	40.00%
Minimum redemption outstanding debt percentage			50.00%
Kronos Worldwide | 9.50% Senior Secured Notes due 2029 | Certain Change Of control events
Debt Instrument [Line Items]
Debt instrument redemption price percent if experiences certain specified change of control events		101.00%	101.00%
Kronos Worldwide | 9.50% Senior Secured Notes due 2029 | Kronos International, Inc
Debt Instrument [Line Items]
Debt instrument interest rate			9.50%		9.50%	9.50%						9.50%
Debt instrument, payment terms					bear interest at 9.50% per annum, payable semi-annually on March 15 and September 15 of each year, payments began on September 15, 2024
Frequency of debt instrument payment		semi-annually	semi-annually
Debt instrument, date of first semi-annual interest payment		--03-15	--03-15
Debt instrument, date of second semi-annual interest payment		--09-15	--09-15
Debt Instrument, date of first required semi-annual payment		Sep. 15, 2024	Sep. 15, 2024
Debt instrument maturity date		Mar. 15, 2029	Mar. 15, 2029
Long term debt, carrying amount					$ 365.4	€ 351,174,000
Unamortized debt issuance costs					6.3
Unamortized premium | €						€ 5,100,000
Debt issuance costs, gross					$ 7.4
Kronos Worldwide | 9.50% Senior Secured Notes due 2029 | Kronos International, Inc | Direct Domestic Subsidiary of KII and Guarantors | Collateral Pledged
Debt Instrument [Line Items]
Parent company ownership interest			100.00%
Kronos Worldwide | 9.50% Senior Secured Notes due 2029 | Kronos International, Inc | Foreign Subsidiary Directly Owned by KII or any Guarantor | Collateral Pledged
Debt Instrument [Line Items]
Parent company ownership interest			65.00%
Kronos Worldwide | 9.50% Senior Secured Notes due 2029 | Kronos International, Inc | Foreign Subsidiary Directly Owned by KII or any Guarantor | Collateral Pledged | Non-voting Common Stock
Debt Instrument [Line Items]
Parent company ownership interest			100.00%
Kronos Worldwide | 3.75% Senior Secured Notes due 2025
Debt Instrument [Line Items]
Debt instrument interest rate			3.75%
Debt instrument principal amount | €			€ 325,000,000
Cash consideration		$ 52.6	48,750,000
Debt instrument, par value | €			1,000
Remaining outstanding | €			75,000,000
Kronos Worldwide | 3.75% Senior Secured Notes due 2025 | Kronos International, Inc
Debt Instrument [Line Items]
Debt instrument interest rate					3.75%	3.75%						3.75%
Debt instrument principal amount | €						€ 75,000,000
Long term debt, carrying amount					$ 78.3							$ 440.9
Interest charge included in interest expense				$ 1.5
Kronos Worldwide | Subordinated, unsecured term loan from Contran
Debt Instrument [Line Items]
Debt instrument interest rate							9.54%	11.50%
Kronos term loan from Contran		53.7	€ 50,000,000		$ 53.7
Kronos Worldwide | Senior notes | Kronos International, Inc
Debt Instrument [Line Items]
Maximum amount of other indebtedness default before triggering customary default provisions		$ 50.0