Investment in TiO2 Manufacturing Joint Venture and Other Assets - Summary of Financial Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financial Information [Line Items]
Current assets	$ 1,453.4	$ 1,425.4
Property and equipment, net	590.4	563.0	$ 563.5
Total assets	2,889.3	2,794.4	2,709.6
Other liabilities, primarily current	39.4	40.0
Total liabilities and equity	2,889.3	2,794.4
Net sales	1,878.1	1,938.4	1,889.3
Cost of sales	1,437.6	1,462.9	1,210.9
General and administrative	283.6	294.2	310.0
Total costs and expenses	1,777.5	1,833.7	1,653.1
Net income	89.0	78.2	301.0
LPC
Financial Information [Line Items]
Current assets	105.8	94.6
Property and equipment, net	134.1	121.3
Total assets	239.9	215.9
Other liabilities, primarily current	30.6	32.8
Partners' equity	209.3	183.1
Total liabilities and equity	239.9	215.9
Net sales	336.1	353.2	332.9
Cost of sales	335.7	352.8	332.5
General and administrative	0.4	0.4	0.4
Total costs and expenses	336.1	353.2	332.9
Net income	0.0	0.0	0.0
LPC | Kronos Worldwide, Inc.
Financial Information [Line Items]
Net sales	167.8	176.2	165.9
LPC | Venator Investments LLC
Financial Information [Line Items]
Net sales	$ 168.3	$ 177.0	$ 167.0