Investment in Kronos Worldwide, Inc. - Selected Financial Information of Kronos Balance Sheet (Detail) - Kronos - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Equity Method Investments [Line Items]
Current assets	$ 1,062.5	$ 650.4
Property and equipment, net	506.4	434.0
Investment in TiO2 joint venture	86.5	78.9
Other noncurrent assets	169.0	16.3
Total assets	1,824.4	1,179.6
Current liabilities	231.5	182.1
Long-term debt	473.8	335.4
Accrued pension and postretirement benefits	261.9	234.2
Other noncurrent liabilities	102.9	32.9
Stockholders' equity	754.3	395.0
Total liabilities and stockholders' equity	$ 1,824.4	$ 1,179.6