Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2017

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, 2016
Noncurrent assets
Valhi common stock	1	$	49,731	$	24,347	$	25,384
December 31, 2017
Noncurrent assets
Valhi common stock	1	$	88,681	$	24,347	$	64,334