Investment in Kronos Worldwide, Inc. - Changes in Carrying Value of Investment (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Balance at the beginning of the year	$ 284,523,000
Equity in earnings (loss) of Kronos Worldwide, Inc.	30,161,000	(31,007,000)	66,437,000
Dividends received from Kronos	(21,132,000)	(21,132,000)	(21,132,000)
Equity in Kronos' other comprehensive income:
Marketable securities	47,112,000	154,169,000	105,419,000	186,451,000
Currency translation	(20,357,000)	1,349,000	(3,606,000)
Balance at the end of the year	237,719,000	284,523,000
Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income:
Defined benefit pension plans/ Other postretirement benefit plans	(18,616,000)	9,758,000	(6,924,000)
OPEB
Equity in Kronos' other comprehensive income:
Defined benefit pension plans/ Other postretirement benefit plans	(993,000)	380,000	(449,000)
Kronos
Balance at the beginning of the year	284,523,000	323,100,000	281,300,000
Equity in earnings (loss) of Kronos Worldwide, Inc.	30,161,000	(31,007,000)	66,437,000
Dividends received from Kronos	(21,132,000)	(21,132,000)	(21,132,000)
Equity in Kronos' other comprehensive income:
Marketable securities	(4,200,000)	2,000,000	(300,000)
Currency translation	(31,300,000)	2,000,000	8,600,000
Other		(200,000)
Balance at the end of the year	237,719,000	284,523,000	323,100,000
Kronos | Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income:
Defined benefit pension plans/ Other postretirement benefit plans	(20,100,000)	8,500,000	(11,600,000)
Kronos | OPEB
Equity in Kronos' other comprehensive income:
Defined benefit pension plans/ Other postretirement benefit plans	$ (300,000)	$ 1,200,000	$ (200,000)