Investment in Kronos Worldwide, Inc. - Selected Financial Information of Kronos Income Statement (Detail) - Kronos - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Schedule Of Equity Method Investments [Line Items]
Net sales	$ 318.4	$ 365.1
Cost of sales	278.0	287.7
Income (loss) from operations	(0.3)	32.2
Income tax expense (benefit)	(1.4)	9.4
Net income (loss)	$ (3.8)	$ 18.4