Investment in Kronos Worldwide, Inc. - Selected Financial Information of Kronos Balance Sheet (Detail) - Kronos - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Schedule Of Equity Method Investments [Line Items]
Current assets	$ 1,195.5	$ 1,062.5
Property and equipment, net	514.1	506.4
Investment in TiO2 joint venture	79.6	86.5
Other noncurrent assets	149.4	169.0
Total assets	1,938.6	1,824.4
Current liabilities	261.1	231.5
Long-term debt	487.4	473.8
Accrued pension and postretirement benefits	267.6	261.9
Other noncurrent liabilities	104.2	102.9
Stockholders' equity	818.3	754.3
Total liabilities and stockholders' equity	$ 1,938.6	$ 1,824.4