Investment in Kronos Worldwide, Inc. - Selected Financial Information of Kronos Income Statement (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Schedule Of Equity Method Investments [Line Items]
Net sales	$ 36,253	$ 23,800	$ 72,177	$ 56,111
Cost of sales	24,947	16,434	49,836	38,314
Income from operations	2,887	14	6,859	2,548
Income tax expense (benefit)	1,901	(1,516)	4,406	(4,779)
Net income	12,697	4,589	25,954	6,499
Kronos
Schedule Of Equity Method Investments [Line Items]
Net sales	478,600	386,000	943,600	807,000
Cost of sales	369,600	290,200	738,900	623,100
Income from operations	43,800	33,000	77,800	76,500
Income tax expense (benefit)	9,200	5,100	15,200	13,500
Net income	$ 25,700	$ 18,600	$ 45,300	$ 45,600