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, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Schedule Of Equity Method Investments [Line Items]
Net sales	$ 336.5	$ 414.8	$ 1,061.8	$ 1,278.4
Cost of sales	293.3	319.1	894.7	1,008.4
Income (loss) from operations	(3.2)	47.9	18.6	118.2
Income tax expense (benefit)	(7.4)	12.3	147.1	27.0
Net income (loss)	$ (11.8)	$ 31.9	$ (153.2)	$ 79.3