Investment in Kronos Worldwide, Inc. - Changes in Carrying Value of Investment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Balance at the beginning of the year	$ 140,695
Equity in earnings (losses) of Kronos	13,171	$ (52,770)	$ 30,161
Dividends received from Kronos	(21,132)	(21,132)	(21,132)
Equity in Kronos' other comprehensive income (loss):
Balance at the end of the year	120,346	140,695
Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans/ Other postretirement benefit plans	1,596	(1,033)	(8,585)
OPEB
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans/ Other postretirement benefit plans	(430)	(386)	(1,205)
Kronos
Balance at the beginning of the year	140,700	237,700	284,500
Equity in earnings (losses) of Kronos	13,200	(52,800)	30,200
Dividends received from Kronos	(21,100)	(21,100)	(21,100)
Equity in Kronos' other comprehensive income (loss):
Marketable securities	700	700	(4,200)
Currency translation	(5,400)	(28,000)	(31,300)
Interest rate swap	100	(700)
Balance at the end of the year	120,300	140,700	237,700
Kronos | Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans/ Other postretirement benefit plans	(7,800)	$ 4,900	(20,100)
Kronos | OPEB
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans/ Other postretirement benefit plans	$ (100)		$ (300)