Carrying amount as of the balance sheet date of the unpaid sum of the known and estimated amounts payable to satisfy all currently due domestic and foreign income tax obligations.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(15)(b)(1))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(15)(1))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(20))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Income Taxes - Additional Information (Detail) $ in Millions, $ in Millions		1 Months Ended	3 Months Ended						6 Months Ended		12 Months Ended
	Dec. 31, 2016 USD ($)	Apr. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2016 CAD ($)
Income Taxes Disclosure [Line Items]
U.S. federal statutory income tax rate											21.00%	35.00%	35.00%
Income tax examination, description											Tax authorities may in the future examine 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 will be resolved in our favor, and therefore our potential exposure, if any, is also uncertain.
Deferred income tax benefit from change in enacted tax rate				$ 59.7							$ 60.6	$ (77.1)
Current income tax expense provisional pursuant to transition tax						$ 76.2
Income tax expense (benefit)											(30.7)	(120.0)	$ 18.6
Increase (decrease) in non-cash deferred income tax asset valuation allowance												(205.4)	(2.2)
Current cash income tax expense for GILTI											4.0
Provision for income taxes includes non-cash deferred income tax expense											$ 6.8
Business interest income, adjusted taxable income											30.00%
Income taxes			$ 9.1			25.1			$ 25.1		$ 9.1	25.1
Non-cash income tax benefit					$ 1.4
Effective state income tax rate											(1.8)
Deferred income taxes expense (benefit)											(115.9)	(245.8)	(26.4)
Unrecognized tax benefits impact on effective tax rate			19.1								19.1
Increase (decrease) in unrecognized tax benefits			3.7								3.7
Accrued interest and penalties during the period											1.3	2.1	1.6
Accrued interest and penalties end of the period			2.2			1.5			1.5		$ 2.2	1.5
US-Canada APA
Income Taxes Disclosure [Line Items]
Current U.S. income tax benefit													$ (3.4)
Canada - Germany APA
Income Taxes Disclosure [Line Items]
U.S.-Canada Advance Pricing Agreement, description											During the third quarter of 2017, Kronos’ Canadian subsidiary executed and finalized an Advance Pricing Agreement with the Competent Authority for Canada (the “Canada-Germany APA”) effective for tax years 2005 - 2017. Pursuant to the terms of the Canada-Germany APA, the Canadian and German tax authorities agreed to certain prior year changes to taxable income of our Canadian and German subsidiaries.
Non-cash income tax benefit related to reversal of reserve for uncertain tax positions							$ 8.1				$ 8.6
IRS
Income Taxes Disclosure [Line Items]
Current cash income tax expense for GILTI			4.0
Earliest Tax Year \| Canada - Germany APA
Income Taxes Disclosure [Line Items]
Effective tax year											2005
Latest Tax Year \| Canada - Germany APA
Income Taxes Disclosure [Line Items]
Effective tax year											2017
Contran
Income Taxes Disclosure [Line Items]
Income taxes payable noncurrent			10.0								$ 10.0
Income taxes payable current			56.3			70.1			70.1		$ 56.3	70.1
Expected Future Periods Net Operating Loss Utilization \| Chemicals
Income Taxes Disclosure [Line Items]
Increase (decrease) in non-cash deferred income tax asset valuation allowance								$ (149.9)
Effect of Currency Exchange Rates
Income Taxes Disclosure [Line Items]
Increase (decrease) in non-cash deferred income tax asset valuation allowance												13.7
Transition Tax \| Maximum
Income Taxes Disclosure [Line Items]
Percentage of annual usage limitation on net operating loss carryforward											80.00%
Germany \| Expected Future Periods Net Operating Loss Utilization \| Chemicals
Income Taxes Disclosure [Line Items]
Increase (decrease) in non-cash deferred income tax asset valuation allowance								(141.9)
Belgium \| Expected Future Periods Net Operating Loss Utilization \| Chemicals
Income Taxes Disclosure [Line Items]
Increase (decrease) in non-cash deferred income tax asset valuation allowance								$ (8.0)
Germany and Belgian
Income Taxes Disclosure [Line Items]
Increase (decrease) in non-cash deferred income tax asset valuation allowance												$ (186.7)
Germany and Belgian \| Current Periods Net Operating Loss Utilization
Income Taxes Disclosure [Line Items]
Increase (decrease) in non-cash deferred income tax asset valuation allowance									(24.1)	$ (12.7)
One Non-U.S. subsidiary \| Expected Future Periods Net Operating Loss Utilization \| Valuation Allowance of Deferred Tax Assets \| Non Cash Deferred Income Tax Benefit
Income Taxes Disclosure [Line Items]
Increase (decrease) in non-cash deferred income tax asset valuation allowance						(18.7)
Kronos Worldwide, Inc. \| Earliest Tax Year \| US-Canada APA
Income Taxes Disclosure [Line Items]
Effective tax year													2005
Kronos Worldwide, Inc. \| Latest Tax Year \| US-Canada APA
Income Taxes Disclosure [Line Items]
Effective tax year													2015
Kronos Worldwide, Inc. \| Expected Future Periods Net Operating Loss Utilization
Income Taxes Disclosure [Line Items]
Increase (decrease) in non-cash deferred income tax asset valuation allowance	$ (173.0)
Kronos Worldwide, Inc. \| Germany \| Expected Future Periods Net Operating Loss Utilization
Income Taxes Disclosure [Line Items]
Increase (decrease) in non-cash deferred income tax asset valuation allowance	(153.0)
Kronos Worldwide, Inc. \| Belgium \| Expected Future Periods Net Operating Loss Utilization
Income Taxes Disclosure [Line Items]
Increase (decrease) in non-cash deferred income tax asset valuation allowance	(20.0)
Kronos Worldwide, Inc. \| Germany and Belgian \| Current Periods Net Operating Loss Utilization
Income Taxes Disclosure [Line Items]
Increase (decrease) in non-cash deferred income tax asset valuation allowance										$ (12.7)
European Subsidiaries \| Transition Tax \| Chemicals
Income Taxes Disclosure [Line Items]
Current income tax expense provisional pursuant to transition tax						76.2
Income tax liability payable period											8 years	8 years
Income tax expense (benefit)				2.1
Aggregate transition tax installments payments made			11.9								$ 11.9
Payable to affiliate			62.2								62.2
European Subsidiaries \| Transition Tax \| Chemicals \| 2017 Tax Year
Income Taxes Disclosure [Line Items]
Current income tax expense paid		$ 6.1
European Subsidiaries \| Transition Tax \| Chemicals \| 2018 Tax Year
Income Taxes Disclosure [Line Items]
Current income tax expense paid											5.8
European Subsidiaries \| Transition Tax \| Chemicals \| Contran
Income Taxes Disclosure [Line Items]
Income taxes payable noncurrent			56.3								56.3
Income taxes payable current			5.9								5.9
European Subsidiaries \| Transition Tax \| Chemicals \| Income Tax Payable \| Contran
Income Taxes Disclosure [Line Items]
Current income tax expense payable in increments over remainder of eight year period			62.2								62.2
European and Canadian Subsidiaries \| Undistributed Earnings Previously Considered to be Permanently Reinvested \| Chemicals
Income Taxes Disclosure [Line Items]
Aggregate provisional non-cash deferred income tax expense						5.3					1.8
Kronos Canadian Subsidiary \| US-Canada APA
Income Taxes Disclosure [Line Items]
Income taxes	$ 2.3												$ 2.3	$ 3
Corporate Tax Purposes \| Kronos Worldwide, Inc. \| Germany \| Chemicals
Income Taxes Disclosure [Line Items]
Net operating loss carryforwards			541.0								541.0
Corporate Tax Purposes \| Kronos Worldwide, Inc. \| Belgium \| Chemicals
Income Taxes Disclosure [Line Items]
Net operating loss carryforwards			$ 16.0								16.0
Canada Revenue Agency and German Federal Central Tax Office \| Germany \| Canada - Germany APA
Income Taxes Disclosure [Line Items]
Non-cash income tax benefit related to increase in German NOLs							2.6
Cash tax refund							$ 0.6
Direct Investment in Subsidiary \| Kronos Worldwide, Inc.
Income Taxes Disclosure [Line Items]
Deferred income tax liability						157.6			157.6			$ 157.6
Deferred income taxes expense (benefit)				$ (112.0)							$ 4.9	22.1	$ 6.5
Direct Investment in Subsidiary \| Kronos Worldwide, Inc. \| Maximum
Income Taxes Disclosure [Line Items]
Deferred income tax liability						$ 155.4			$ 155.4			$ 155.4