Investment in Kronos Worldwide, Inc. - Changes in Carrying Value of Investment (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Balance at the beginning of the period			$ 120,346
Equity in earnings of Kronos	$ 22,437	$ 6,776	93,357	$ 6,123
Dividends received from Kronos			(15,849)	$ (15,849)
Equity in Kronos' other comprehensive income (loss):
Balance at the end of the period	216,301		216,301
Kronos
Balance at the beginning of the period			120,300
Equity in earnings of Kronos			93,400
Dividends received from Kronos			(15,800)
Equity in Kronos' other comprehensive income (loss):
Marketable securities			(400)
Currency translation			16,300
Interest rate swap			600
Balance at the end of the period	$ 216,300		216,300
Kronos | Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans			$ 1,900