Income Taxes - Additional Information (Detail) CAD in Millions, $ in Millions		3 Months Ended						6 Months Ended	12 Months Ended
	Jun. 30, 2015 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2016 CAD	Dec. 31, 2013 CAD
Income Taxes Disclosure [Line Items]
U.S. federal statutory income tax rate									35.00%	35.00%	35.00%
Income taxes		$ 5.1			$ 5.7			$ 5.7	$ 5.1	$ 5.7
Unrecognized tax benefits impact on effective tax rate		30.9			23.4			23.4	30.9	23.4	$ 24.2
Increase (decrease) in unrecognized tax benefits		14.3							14.3
Accrued interest and penalties during the period									1.6	1.3	1.2
Accrued interest and penalties end of the period		5.2			4.2			4.2	5.2	4.2
Deferred income taxes expense (benefit)									$ (31.0)	86.4	9.9
U.S. Income Tax Audit
Income Taxes Disclosure [Line Items]
Non-cash income tax benefit recognized related to completion of audit											3.1
Canada | Canadian Income Tax Audit
Income Taxes Disclosure [Line Items]
Non-cash income tax benefit recognized related to completion of audit											$ 3.0
Kronos Worldwide, Inc. | US-Canada APA
Income Taxes Disclosure [Line Items]
U.S.-Canada Advance Pricing Agreement, 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 will be resolved in our favor, and therefore our potential exposure, if any, is also uncertain.  In 2011 and 2012 Kronos received notices of re-assessment from the Canadian federal and provincial tax authorities related to the years 2002 through 2004. We objected to the re-assessments and believed the position was without merit. Accordingly, we appealed the re-assessments and in connection with such appeal we were required to post letters of credit aggregating Cdn. $7.9 million. In 2014, the Appeals Division of the Canadian Revenue Authority ruled in our favor and reversed in their entirety such notices of re-assessment. As a result, we recognized a non-cash income tax benefit of $3.0 million related to the release of a portion of our reserve for uncertain tax positions in 2014 related to the completion of this Canadian income tax audit. In addition, the related letters of credit have been cancelled.  Also during 2014, we recognized a non-cash income tax benefit of $3.1 million related to the release of a portion of our reserve for uncertain tax positions in conjunction with the completion of an audit of our U.S. income tax return for 2009.  As a result of ongoing audits in certain jurisdictions, in 2008 Kronos filed Advance Pricing Agreement Requests with the tax authorities in the U.S., Canada and Germany. These requests have been under review with the respective tax authorities since 2008 and prior to 2016, it was uncertain whether an agreement would be reached between the tax authorities and whether we would agree to execute and finalize such agreements. During 2016, Contran, as the ultimate parent of our U.S. Consolidated income tax group, executed and finalized an Advance Pricing Agreement with the U.S. Internal Revenue Service and our Canadian subsidiary executed and finalized an Advance Pricing Agreement with the Competent Authority for Canada (collectively, the “U.S.-Canada APA”) effective for tax years 2005 - 2015.
U.S Income tax benefit									$ 3.4
Kronos Worldwide, Inc. | US-Canada APA | Earliest Tax Year
Income Taxes Disclosure [Line Items]
Effective tax year									2005
Kronos Worldwide, Inc. | US-Canada APA | Latest Tax Year
Income Taxes Disclosure [Line Items]
Effective tax year									2015
Kronos Worldwide, Inc. | Bank Of Montreal
Income Taxes Disclosure [Line Items]
Letter of credit collateralized | CAD													CAD 7.9
Kronos Worldwide, Inc. | Direct investment in subsidiary excess carrying amount
Income Taxes Disclosure [Line Items]
Deferred income taxes expense (benefit)					$ (29.3)	$ (29.3)	$ (29.3)		$ 6.5
Kronos Worldwide, Inc. | Germany | Corporate Tax Purposes
Income Taxes Disclosure [Line Items]
Net operating loss carryforwards		638.0							638.0
Kronos Worldwide, Inc. | Germany | Trade Tax Purposes
Income Taxes Disclosure [Line Items]
Net operating loss carryforwards		71.0							71.0
Kronos Worldwide, Inc. | Belgium | Corporate Tax Purposes
Income Taxes Disclosure [Line Items]
Net operating loss carryforwards		93.0							93.0
Kronos Worldwide, Inc. | Germany and Belgian
Income Taxes Disclosure [Line Items]
Deferred income tax asset valuation allowance	$ 150.3							$ 8.7	(2.2)	(159.0)
Increase in deferred income tax asset valuation allowance									6.7	$ 9.8
Deferred income taxes expense (benefit)		(4.3)	$ (0.8)	$ 2.9
Kronos Canadian Subsidiary | US-Canada APA
Income Taxes Disclosure [Line Items]
Income taxes		$ 2.3							$ 2.3			CAD 3.0