Investment in Kronos Worldwide, Inc. - Changes in Carrying Value of Investment (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Balance at the beginning of the period	$ 229,543
Equity in earnings of Kronos	21,479	$ 11,175
Dividends received from Kronos	(5,987)	$ (5,283)
Equity in Kronos' other comprehensive income:
Balance at the end of the period	249,028
Kronos
Balance at the beginning of the period	229,500
Equity in earnings of Kronos	21,500
Dividends received from Kronos	(6,000)
Equity in Kronos' other comprehensive income:
Currency translation	3,300
Balance at the end of the period	249,000
Kronos \| Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income:
Defined benefit pension plans	$ 700

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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