Investment in Kronos Worldwide, Inc. - Change in Carrying Value of Investment (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Schedule Of Change In Carrying Value Of Equity Investment [Line Items]
Balance at the beginning of the period			$ 281,257,000
Equity in earnings of Kronos	10,715,000	26,097,000	71,951,000	71,487,000
Dividends received from Kronos			(15,849,000)	(32,578,000)
Balance at the end of the period	339,393,000		339,393,000
Investment In Kronos Worldwide Inc [Member]
Schedule Of Change In Carrying Value Of Equity Investment [Line Items]
Balance at the beginning of the period			281,300,000
Equity in earnings of Kronos			72,000,000
Dividends received from Kronos			(15,800,000)
Other, principally equity in other comprehensive income items of Kronos			1,900,000
Balance at the end of the period	$ 339,400,000		$ 339,400,000