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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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Balance at the beginning of the period			$ 255,565
Equity in earnings of Kronos Worldwide, Inc.	$ 5,463	$ 9,905	23,632	$ 55,029
Dividends received from Kronos			(19,017)	$ (17,961)
Equity in Kronos' other comprehensive income:
Balance at the end of the period	257,717		257,717
Kronos
Balance at the beginning of the period			255,500
Equity in earnings of Kronos Worldwide, Inc.			23,600
Dividends received from Kronos			(19,000)
Equity in Kronos' other comprehensive income:
Currency translation			(3,500)
Equity in Kronos' treasury stock acquired			(900)
Balance at the end of the period	$ 257,700		257,700
Kronos \| Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income:
Defined benefit pension plans			$ 2,000