Investment in Kronos Worldwide, Inc. - Changes in Carrying Value of Investment (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Balance at the beginning of the period	$ 242,374
Equity in earnings of Kronos Worldwide, Inc.	5,968	$ 8,207
Dividends received from Kronos	(6,339)	$ (6,339)
Equity in Kronos' other comprehensive income:
Balance at the end of the period	243,732
Kronos
Balance at the beginning of the period	242,400
Equity in earnings of Kronos Worldwide, Inc.	6,000
Dividends received from Kronos	(6,300)
Equity in Kronos' other comprehensive income:
Currency translation	600
Balance at the end of the period	243,700
Kronos \| Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income:
Defined benefit pension plans	$ 1,000

Amount of distribution received from equity method investee for return on investment, classified as operating activities. Excludes distribution for return of investment, classified as investing activities.

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