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Investment in Kronos Worldwide, Inc. - Changes in Carrying Value of Investment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Balance at the beginning of the period			$ 255,565
Equity in earnings of Kronos Worldwide, Inc.	$ 8,944	$ 23,645	18,169	$ 45,124
Dividends received from Kronos			(12,678)	$ (11,974)
Equity in Kronos' other comprehensive income:
Balance at the end of the period	264,118		264,118
Kronos
Balance at the beginning of the period			255,500
Equity in earnings of Kronos Worldwide, Inc.			18,200
Dividends received from Kronos			(12,700)
Equity in Kronos' other comprehensive income:
Currency translation			2,100
Equity in Kronos' treasury stock acquired			(400)
Balance at the end of the period	$ 264,100		264,100
Kronos \| Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income:
Defined benefit pension plans			$ 1,400