Income Taxes - Additional Information (Detail) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended		3 Months Ended
	Mar. 31, 2014 USD ($)	Jun. 30, 2014 CAD	Jun. 30, 2014 USD ($)	Mar. 31, 2014 Net of noncontrolling interest USD ($)	Jun. 30, 2014 Canadian Income Tax Audit USD ($)	Jun. 30, 2014 U.S. Income Tax Audit USD ($)	Jun. 30, 2014 Kronos Worldwide, Inc. Bank Of Montreal CAD	Dec. 31, 2013 Kronos Worldwide, Inc. Bank Of Montreal CAD
Income Taxes Disclosure [Line Items]
Letter of credit collateralized		0.3					0.3	7.9
Unrecognized tax benefits			8.8
Non-cash income tax benefit recognized related to release of portion of reserve for uncertain tax positions					3.0	3.1
Aggregate letters of credit cancelled		7.6
Provision for income taxes related to previous periods	$ 1.0			$ 0.9