Investment in Kronos Worldwide, Inc. - Selected Financial Information of Kronos Income Statement (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Schedule Of Equity Method Investments [Line Items]
Net sales	$ 23,800	$ 33,730	$ 56,111	$ 64,907
Cost of sales	16,434	22,791	38,314	44,344
Income from operations	14	(12,889)	2,548	(10,371)
Net income	4,589	5,878	6,499	21,082
Kronos
Schedule Of Equity Method Investments [Line Items]
Net sales	386,000	484,500	807,000	921,000
Cost of sales	290,200	375,000	623,100	702,200
Income from operations	33,000	46,500	76,500	95,500
Income tax expense	5,100	11,400	13,500	24,200
Net income	$ 18,600	$ 29,500	$ 45,600	$ 59,800