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Investment in Kronos Worldwide, Inc. - Changes in Carrying Value of Investment (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Balance at the beginning of the period			$ 229,543
Equity in earnings of Kronos	$ 9,905	$ 22,437	55,029	$ 93,357
Dividends received from Kronos			(17,961)	$ (15,849)
Equity in Kronos' other comprehensive income:
Balance at the end of the period	265,776		265,776
Kronos
Balance at the beginning of the period			229,500
Equity in earnings of Kronos			55,000
Dividends received from Kronos			(17,900)
Equity in Kronos' other comprehensive income:
Currency translation			(3,000)
Balance at the end of the period	$ 265,800		265,800
Kronos \| Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income:
Defined benefit pension plans			$ 2,200