Investment in TiO2 Manufacturing Joint Venture and Other Assets - Summary of Financial Information (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2013
Financial Information [Line Items]
Current assets	$ 896.2				$ 1,048.6				$ 896.2	$ 1,048.6
Property and equipment, net	665.7				733.6				665.7	733.6	$ 796.4
Total assets	2,537.4				2,945.2				2,537.4	2,945.2	2,951.7
Other liabilities, primarily current	30.4				40.4				30.4	40.4
Total liabilities and equity	2,537.4				2,945.2				2,537.4	2,945.2
Net sales	324.8	$ 383.2	$ 408.8	$ 416.1	432.0	$ 476.5	$ 491.7	$ 462.4	1,532.9	1,862.6	1,863.6
Cost of sales									1,310.0	1,459.8	1,729.4
General and administrative									269.7	276.1	375.1
Total costs and expenses									1,638.7	1,792.6	2,169.5
Net income (loss)	(35.7)	$ (13.3)	$ (139.4)	$ 17.3	13.7	$ 37.5	$ 23.7	$ 4.6	(171.1)	79.5	(126.9)
Loss before income taxes									(73.8)	112.0	(217.9)
LPC
Financial Information [Line Items]
Current assets	96.2				107.4				96.2	107.4
Property and equipment, net	110.1				110.6				110.1	110.6
Total assets	206.3				218.0				206.3	218.0
Other liabilities, primarily current	37.8				37.3				37.8	37.3
Partners’ equity	168.5				180.7				168.5	180.7
Total liabilities and equity	$ 206.3				$ 218.0				206.3	218.0
Net sales									339.0	386.9	449.1
Cost of sales									338.5	386.4	448.7
General and administrative									0.5	0.5	0.4
Total costs and expenses									339.0	386.9	449.1
LPC | Kronos Worldwide, Inc.
Financial Information [Line Items]
Net sales									176.5	193.1	224.5
LPC | Tioxide
Financial Information [Line Items]
Net sales									$ 162.5	$ 193.8	$ 224.6
Basic Management Inc And Landwell
Financial Information [Line Items]
Net sales												$ 9.5
Net income (loss)												(3.7)
Loss before income taxes												$ (3.9)