Income Taxes - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended					12 Months Ended
	Mar. 27, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes Disclosure [Line Items]
Income tax examination, description							Tax authorities are examining certain of our U.S. and non-U.S. tax returns and have or may propose tax deficiencies, including penalties and interest. Because of the inherent uncertainties involved in settlement initiatives and court and tax proceedings, we cannot guarantee that these tax matters, if any, will be resolved in our favor, and therefore our potential exposure, if any, is also uncertain.
Income tax expense (benefit)							$ 15.9	$ 26.5	$ (30.7)
Provision for income taxes includes non-cash deferred income tax expense							$ 3.3	4.5	6.8
Business interest income, adjusted taxable income	30.00%						30.00%
Current income taxes expense (benefit)							$ 28.2	26.3	85.2
Deferred income taxes expense (benefit)							(12.3)	0.2	(115.9)
Deferred income tax benefit from change in enacted tax rate							(0.2)	4.7	58.8
Non-cash income tax benefit					$ 1.4
Aggregate provisional non-cash deferred income tax expense									(1.8)
Deferred income taxes			$ 38.1				29.6	38.1
CARES act of 2020, Business interest income, adjusted taxable income	50.00%
Cash tax benefit recognized		$ 1.0
Unrecognized tax benefits impact on effective tax rate							9.4
Increase (decrease) in unrecognized tax benefits							3.6
Accrued interest and penalties during the period							0.8	1.3	$ 1.3
Accrued interest and penalties end of the period			1.9				1.3	1.9
Contran
Income Taxes Disclosure [Line Items]
Income taxes payable noncurrent			4.0				8.3	4.0
Income taxes payable current			56.3				$ 50.4	56.3
Germany
Income Taxes Disclosure [Line Items]
Income tax expense (benefit)			3.0
Current income taxes expense (benefit)			1.5
Deferred income taxes expense (benefit)			1.5
Deferred income tax benefit from change in enacted tax rate			$ 4.7
European Subsidiaries | Chemicals | Transition Tax
Income Taxes Disclosure [Line Items]
Current income tax expense provisional pursuant to transition tax						$ 76.2
Income tax expense (benefit)				$ 2.1
Income tax liability payable period							8 years		8 years
Payable to affiliate							$ 56.3
European Subsidiaries | Chemicals | Transition Tax | Contran
Income Taxes Disclosure [Line Items]
Income taxes payable noncurrent							50.4
Income taxes payable current							5.9
European Subsidiaries | Chemicals | Income Tax Payable | Transition Tax | Contran
Income Taxes Disclosure [Line Items]
Current income tax expense payable in increments over remainder of eight year period							56.3
Corporate Tax Purposes | Kronos Worldwide, Inc. | Germany | Chemicals
Income Taxes Disclosure [Line Items]
Net operating loss carryforwards							531.0
Corporate Tax Purposes | Kronos Worldwide, Inc. | Belgium | Chemicals
Income Taxes Disclosure [Line Items]
Net operating loss carryforwards							20.0
Direct Investment in Subsidiary | Kronos Worldwide, Inc.
Income Taxes Disclosure [Line Items]
Deferred income taxes expense (benefit)				$ (112.0)			2.4	$ 0.1	$ 4.9
Deferred income taxes							35.5
Direct Investment in Subsidiary | Kronos Worldwide, Inc. | Maximum
Income Taxes Disclosure [Line Items]
Deferred income taxes							$ 155.4