Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2018

Investments Debt And Equity Securities [Abstract]

Schedule of Marketable Securities

	Fair value measurement level	Market value		Cost basis		Unrealized gain
		(In thousands)
December 31, 2017
Valhi common stock	1	$	88,681	$	24,347	$	64,334
March 31, 2018
Valhi common stock	1	$	87,100	$	24,347	$	62,753