Investment in Kronos Worldwide, Inc. - Selected Financial Information of Kronos Balance Sheet (Detail) - Kronos - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Schedule Of Equity Method Investments [Line Items]
Current assets	$ 1,021.2	$ 650.4
Property and equipment, net	486.2	434.0
Investment in TiO2 joint venture	75.1	78.9
Deferred income taxes	120.0	8.1
Other noncurrent assets	7.9	8.2
Total assets	1,710.4	1,179.6
Current liabilities	240.0	182.1
Long-term debt	467.5	335.4
Accrued pension and postretirement benefits	261.6	234.2
Other noncurrent liabilities	30.6	32.9
Stockholders' equity	710.7	395.0
Total liabilities and stockholders' equity	$ 1,710.4	$ 1,179.6