Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2020

Investments Debt And Equity Securities [Abstract]

Schedule of Marketable Securities

	Fair value measurement level	Market value		Cost basis		Unrealized gain (loss)
		(In thousands)
December 31, 2019
Valhi common stock	1	$	26,877	$	24,347	$	2,530
June 30, 2020
Valhi common stock	1	$	12,552	$	24,347	$	(11,795	)