Investment in Kronos Worldwide, Inc. - Selected Financial Information of Kronos Income Statement (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Schedule of Equity Method Investments [Line Items]
Net sales	$ 37,110	$ 35,736	$ 110,239	$ 105,755
Cost of sales	26,948	27,202	80,578	78,704
Income from operations	2,106	12,888	4,199	9,576
Net income	10,347	27,815	57,839	62,632
Kronos Worldwide Inc [Member]
Schedule of Equity Method Investments [Line Items]
Net sales	472,900	548,000	1,579,500	1,505,900
Cost of sales	386,900	337,100	1,068,700	951,600
Income from operations	38,500	156,600	358,500	403,200
Net income	$ 35,200	$ 85,900	$ 236,600	$ 235,200