Investment in Kronos Worldwide, Inc. - Changes in Carrying Value of Investment (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Balance at the beginning of the period			$ 237,719
Equity in losses of Kronos	$ (3,600)	$ 9,689	(46,584)	$ 24,101
Dividends received from Kronos			(15,849)	(15,849)
Equity in Kronos' other comprehensive income:
Marketable securities	5,455	48,327	5,455	48,327	$ 39,968	$ 47,112	$ 47,305	$ 154,169
Currency translation	(3,538)	$ (9,215)	(15,309)	$ (10,589)
Interest rate swap	(733)		(733)
Balance at the end of the period	154,588		154,588
Kronos
Balance at the beginning of the period			237,700
Equity in losses of Kronos			(46,600)
Dividends received from Kronos			(15,800)
Equity in Kronos' other comprehensive income:
Marketable securities	900		900
Currency translation			(23,600)
Interest rate swap			(1,100)
Balance at the end of the period	$ 154,600		154,600
Kronos | Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income:
Defined benefit pension plans/ Other postretirement benefit plans			$ 3,100