Investment in Kronos Worldwide, Inc. - Selected Financial Information of Kronos Income Statement (Detail) - Kronos - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Equity Method Investments [Line Items]
Net sales	$ 1,364.3	$ 1,348.8	$ 1,651.9
Cost of sales	1,107.3	1,156.5	1,302.2
Income (loss) from operations	81.1	(1.1)	149.7
Income tax expense	17.9	142.8	34.5
Net income (loss)	$ 43.3	$ (173.6)	$ 99.2