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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Schedule Of Equity Method Investments [Line Items]
Net sales	$ 356.1	$ 336.5	$ 1,030.6	$ 1,061.8
Cost of sales	280.6	293.3	859.2	894.7
Income (loss) from operations	28.0	(3.2)	38.2	18.6
Income tax expense (benefit)	0.7	(7.4)	3.2	147.1
Net income (loss)	$ 22.2	$ (11.8)	$ 20.1	$ (153.2)