Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2021

Investments Debt And Equity Securities [Abstract]

Schedule of Marketable Securities

	Fair value
	measurement	Market		Cost		Unrealized
	level	value		basis		gain (loss)
		(In thousands)
December 31, 2020
Noncurrent assets
Valhi common stock	1	$	18,206	$	24,347	$	(6,141)
December 31, 2021
Noncurrent assets
Valhi common stock	1	$	34,435	$	24,347	$	10,088