Investment in Kronos Worldwide, Inc. - Changes in Carrying Value of Investment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Balance at the beginning of the period	$ 120,346
Equity in earnings of Kronos	11,175	$ (1,150)
Dividends received from Kronos	(5,283)	$ (5,283)
Equity in Kronos' other comprehensive income (loss):
Balance at the end of the period	130,002
Kronos
Balance at the beginning of the period	120,300
Equity in earnings of Kronos	11,200
Dividends received from Kronos	(5,300)
Equity in Kronos' other comprehensive income (loss):
Marketable securities	(100)
Currency translation	2,700
Interest rate swap	200
Balance at the end of the period	130,000
Kronos | Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans	$ 1,000