Investment in Kronos Worldwide, Inc. - Changes in Carrying Value of Investment (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Balance at the beginning of the period			$ 140,695
Equity in earnings of Kronos	$ 6,776	$ (3,600)	6,123	$ (46,584)
Dividends received from Kronos			(15,849)	(15,849)
Equity in Kronos' other comprehensive income (loss):
Balance at the end of the period	138,550		138,550
Kronos
Balance at the beginning of the period			140,700
Equity in earnings of Kronos			6,100
Dividends received from Kronos			(15,800)	$ (15,800)
Equity in Kronos' other comprehensive income (loss):
Marketable securities			300
Currency translation			5,600
Interest rate swap			(900)
Balance at the end of the period	$ 138,550		138,550
Kronos | Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans			$ 2,600