Investment in Kronos Worldwide, Inc. - Changes in Carrying Value of Investment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Balance at the beginning of the period	$ 140,695
Equity in losses of Kronos	(1,150)	$ 5,605
Dividends received from Kronos	(5,283)	(5,283)
Equity in Kronos' other comprehensive income (loss):
Balance at the end of the period	138,515
Kronos
Balance at the beginning of the period	140,700
Equity in losses of Kronos	(1,200)
Dividends received from Kronos	(5,283)	$ (5,283)
Equity in Kronos' other comprehensive income (loss):
Currency translation	4,400
Interest rate swap	(900)
Balance at the end of the period	138,500
Kronos | Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans	$ 800