Investment in Kronos Worldwide, Inc. - Selected Financial Information of Kronos Balance Sheet (Detail) - Kronos - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Schedule Of Equity Method Investments [Line Items]
Current assets	$ 1,238.4	$ 1,062.5
Property and equipment, net	491.9	506.4
Investment in TiO2 joint venture	79.7	86.5
Other noncurrent assets	124.9	169.0
Total assets	1,934.9	1,824.4
Current liabilities	249.6	231.5
Long-term debt	465.2	473.8
Accrued pension and postretirement benefits	255.0	261.9
Other noncurrent liabilities	91.7	102.9
Stockholders' equity	873.4	754.3
Total liabilities and stockholders' equity	$ 1,934.9	$ 1,824.4