Investment in Kronos Worldwide, Inc. - Changes in Carrying Value of Investment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Balance at the beginning of the year	$ 229,543
Equity in earnings of Kronos Worldwide, Inc.	62,316	$ 107,785	$ 13,171
Dividends received from Kronos	(23,948)	(21,132)	(21,132)
Equity in Kronos' other comprehensive income (loss):
Balance at the end of the year	255,565	229,543
Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans/ Other postretirement benefit plans	(772)	2,202	1,596
Kronos
Balance at the beginning of the year	229,500	120,300	140,700
Equity in earnings of Kronos Worldwide, Inc.	62,300	107,800	13,200
Dividends received from Kronos	(23,900)	(21,100)	(21,100)
Equity in Kronos' other comprehensive income (loss):
Marketable securities		900	700
Currency translation	(10,100)	17,500	(5,400)
Interest rate swap		600	100
Other		100
Balance at the end of the year	255,500	229,500	120,300
Kronos | Defined Benefit Pension Plans
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans/ Other postretirement benefit plans	(2,200)	3,600	(7,800)
Kronos | OPEB
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans/ Other postretirement benefit plans	$ (100)	$ (200)	$ (100)