Investment in Kronos Worldwide, Inc. - Changes in Carrying Value of Investment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Balance at the beginning of the period			$ 237,719
Equity in losses of Kronos	$ (48,589)	$ 10,069	(42,984)	$ 14,412
Dividends received from Kronos			(10,566)	(10,566)
Other comprehensive income (loss), net of tax:
Marketable securities	39,968	47,305	39,968	47,305	$ 45,326	$ 47,112	$ 70,238	$ 154,169
Currency translation	1,188	$ (860)	(11,771)	$ (1,374)
Balance at the end of the period	167,941		167,941
Kronos
Balance at the beginning of the period			237,719
Equity in losses of Kronos			(43,000)
Dividends received from Kronos			(10,600)
Other comprehensive income (loss), net of tax:
Marketable securities	(200)		(200)
Currency translation			(18,100)
Balance at the end of the period	$ 167,941		167,941
Kronos | Defined Benefit Pension Plans
Other comprehensive income (loss), net of tax:
Defined benefit pension plans/ Other postretirement benefit plans			$ 2,100