Investment in Kronos Worldwide, Inc. - Selected Financial Information of Kronos Income Statement (Detail) - Kronos - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Schedule Of Equity Method Investments [Line Items]
Net sales	$ 437.4	$ 410.3	$ 1,358.4	$ 1,312.5
Cost of sales	349.7	291.2	1,051.9	846.8
Income from operations	33.1	58.1	128.6	285.5
Income tax expense	6.3	14.1	30.5	75.5
Net income	$ 17.9	$ 32.6	$ 77.7	$ 181.0