Investment in Kronos Worldwide, Inc. - Selected Financial Information of Kronos Income Statement (Detail) - Kronos - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Equity Method Investments [Line Items]
Net sales	$ 1,348.8	$ 1,651.9	$ 1,732.4
Cost of sales	1,156.5	1,302.2	1,620.2
Income (loss) from operations	(1.1)	149.7	(132.6)
Income tax expense (benefit)	142.8	34.5	(57.9)
Net income (loss)	$ (173.6)	$ 99.2	$ (102.0)