Investment in Kronos Worldwide, Inc. - Changes in Carrying Value of Investment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Balance at the beginning of the year	$ 255,565
Equity in earnings of Kronos Worldwide, Inc.	26,470	$ 62,316	$ 107,785
Dividends received from Kronos	(25,356)	(23,948)	(21,132)
Equity in Kronos' other comprehensive income (loss):
Balance at the end of the year	248,355	255,565
Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans/ Other postretirement benefit plans	2,914	(772)	2,202
Kronos
Balance at the beginning of the year	255,500	229,500	120,300
Equity in earnings of Kronos Worldwide, Inc.	26,500	62,300	107,800
Dividends received from Kronos	(25,400)	(23,900)	(21,100)
Equity in Kronos' other comprehensive income (loss):
Currency translation	(500)	(10,100)	17,500
Marketable securities			900
Interest rate swap			600
Other	(900)		100
Balance at the end of the year	248,400	255,500	229,500
Kronos | Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans/ Other postretirement benefit plans	(6,700)	(2,200)	3,600
Kronos | OPEB
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans/ Other postretirement benefit plans	$ (100)	$ (100)	$ (200)