Long-Term Debt - Revolving Credit Facility - Additional Information (Detail) - Kronos Worldwide, Inc. $ in Millions	1 Months Ended		8 Months Ended	9 Months Ended
	Sep. 30, 2017 USD ($)	Jan. 31, 2017	Sep. 13, 2017	Sep. 30, 2017 USD ($)	Sep. 30, 2017 EUR (€)
Foreign Line of Credit | Europe
Line Of Credit Facility [Line Items]
Amount available for borrowing	$ 106.1			$ 106.1	€ 90,000,000
European Revolving Credit Facility
Line Of Credit Facility [Line Items]
Line of credit facility amended month and year				2017-09
Line of credit maturity	Sep. 30, 2022
Line of credit facility, maturity period	5 years
Line of credit maximum borrowing capacity | €					90,000,000
European Revolving Credit Facility | EURIBOR
Line Of Credit Facility [Line Items]
Interest rate on outstanding borrowings	1.60%
European Revolving Credit Facility Superseded
Line Of Credit Facility [Line Items]
Line of credit maximum borrowing capacity | €					€ 120,000,000
European Revolving Credit Facility Superseded | EURIBOR
Line Of Credit Facility [Line Items]
Interest rate on outstanding borrowings	1.90%
North American Revolving Credit Facility
Line Of Credit Facility [Line Items]
Line of credit maturity, description				In January 2017, Kronos extended the maturity date of its North American revolving credit facility to the earlier of (i) January 30, 2022 or (ii) 90 days prior to the maturity date of our existing term loan indebtedness (or 90 days prior to the maturity date of any indebtedness incurred in a permitted refinancing of such existing term loan indebtedness). The issuance of the Senior Notes is a permitted refinancing of our term loan, and accordingly, the maturity date of the North American revolving credit facility is January 30, 2022.
Borrowings under credit facility during the period				$ 253.9
Repayments of lines of credit				253.9
Debt instrument, average interest rate during period			4.80%
Repayments of line of credit using Senior Notes proceeds	$ 21.0
Amount available for borrowing	$ 100.0			$ 100.0
North American Revolving Credit Facility | Maturity Date Option 1
Line Of Credit Facility [Line Items]
Line of credit, maturity date				Jan. 30, 2022
North American Revolving Credit Facility | Maturity Date Option 2
Line Of Credit Facility [Line Items]
Line of credit, maturity date				Jan. 30, 2022
Maturity date of term loan		90 days
Maturity date permitted refinancing of term loan		90 days