Investment in Kronos Worldwide, Inc. - Selected Financial Information of Kronos Income Statement (Detail) - Kronos - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Schedule Of Equity Method Investments [Line Items]
Net sales	$ 356.1	$ 360.2	$ 674.5	$ 725.3
Cost of sales	300.6	313.7	578.6	601.4
Income (loss) from operations	10.5	(10.4)	10.2	21.8
Income tax expense	3.9	145.1	2.5	154.5
Net income (loss)	$ 1.7	$ (159.8)	$ (2.1)	$ (141.4)