Investment in Kronos Worldwide, Inc. - Changes in Carrying Value of Investment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Balance at the beginning of the year	$ 237,719
Equity in earnings (losses) of Kronos	(52,770)	$ 30,161	$ (31,007)
Dividends received from Kronos	(21,132)	(21,132)	(21,132)
Equity in Kronos' other comprehensive income (loss):
Currency translation	(18,211)	(20,357)	1,349
Interest rate swap	(445)
Balance at the end of the year	140,695	237,719
Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans/ Other postretirement benefit plans	2,548	(18,616)	9,758
OPEB
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans/ Other postretirement benefit plans	(294)	(993)	380
Kronos
Balance at the beginning of the year	237,700	284,500	323,100
Equity in earnings (losses) of Kronos	(52,800)	30,200	(31,000)
Dividends received from Kronos	(21,100)	(21,100)	(21,100)
Equity in Kronos' other comprehensive income (loss):
Marketable securities	700	(4,200)	2,000
Currency translation	(28,000)	(31,300)	2,000
Interest rate swap	(700)
Other			(200)
Balance at the end of the year	140,700	237,700	284,500
Kronos | Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans/ Other postretirement benefit plans	$ 4,900	(20,100)	8,500
Kronos | OPEB
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans/ Other postretirement benefit plans		$ (300)	$ 1,200