Investment in Kronos Worldwide, Inc. - Changes in Carrying Value of Investment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Balance at the beginning of the period			$ 120,346
Equity in earnings of Kronos	$ 59,745	$ 497	70,920	$ (653)
Dividends received from Kronos			(10,566)	$ (10,566)
Equity in Kronos' other comprehensive income (loss):
Balance at the end of the period	188,969		188,969
Kronos
Balance at the beginning of the period			120,300
Equity in earnings of Kronos			70,900
Dividends received from Kronos			(10,600)
Equity in Kronos' other comprehensive income (loss):
Marketable securities			(100)
Currency translation			7,200
Interest rate swap			100
Balance at the end of the period	$ 189,000		189,000
Kronos | Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans			$ 1,200