Income Taxes - Additional Information (Detail) CAD in Millions, $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 CAD	Dec. 31, 2015 USD ($)
Income Taxes Disclosure [Line Items]
U.S. federal statutory income tax rate	35.00%	35.00%			35.00%	35.00%
Income taxes	$ 5.4				$ 5.4			$ 5.7
Non-cash income tax benefit recognized related to release of portion of reserve for uncertain tax positions				$ 2.4
Increase (decrease) in unrecognized tax benefits	(10.7)				(10.7)
Deferred income taxes expense (benefit)					(15.5)	$ 90.2
Kronos Worldwide, Inc. | Direct investment in subsidiary excess carrying amount
Income Taxes Disclosure [Line Items]
Deferred income taxes expense (benefit)					$ 9.1	$ (29.7)
Kronos Worldwide, Inc. | Germany and Belgium
Income Taxes Disclosure [Line Items]
Deferred income tax asset valuation allowance	2.1	$ 2.3	$ 150.3
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 matters will be resolved in our favor, and therefore our potential exposure, if any, is also uncertain. 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 the third quarter of 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 the third quarter of 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 Kronos’ 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	5.5				$ 5.5
Kronos Canadian Subsidiary | US-Canada APA
Income Taxes Disclosure [Line Items]
Income taxes	$ 2.3				$ 2.3		CAD 3
Kronos Canadian Subsidiary | US-Canada APA | Canada Revenue Agency | Earliest Tax Year
Income Taxes Disclosure [Line Items]
Effective tax year	2005
Kronos Canadian Subsidiary | US-Canada APA | Canada Revenue Agency | Latest Tax Year
Income Taxes Disclosure [Line Items]
Effective tax year	2015