CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Net sales	$ 29,703	$ 30,029	$ 94,610	$ 90,827
Cost of sales	20,227	20,433	64,571	60,494
Gross margin	9,476	9,596	30,039	30,333
Selling, general and administrative expense	5,210	5,075	15,860	15,455
Other operating income (expense):
Insurance recoveries	243	526	5,240	889
Other income, net	4,424	18	4,433	645
Litigation settlement expense, net	305		(19,266)	(62,000)
Corporate expense	(3,429)	(1,583)	(9,148)	(14,352)
Income (loss) from operations	5,809	3,482	(4,562)	(59,940)
Equity in earnings of Kronos Worldwide, Inc.	5,463	9,905	23,632	55,029
Other income (expense):
Marketable equity securities	(15,379)	(35,645)	(431)	(55,911)
Other components of net periodic pension and OPEB cost	(434)	(99)	(1,290)	(297)
Interest and dividend income	1,571	1,336	5,213	3,630
Interest expense	(314)	(9)	(332)	(25)
Income (loss) before income taxes	(3,284)	(21,030)	22,230	(57,514)
Income tax expense (benefit)	(2,286)	(6,158)	942	(15,416)
Net income (loss)	(998)	(14,872)	21,288	(42,098)
Noncontrolling interest in net income of subsidiary	540	514	1,744	1,654
Net income (loss) attributable to NL stockholders	$ (1,538)	$ (15,386)	$ 19,544	$ (43,752)
Amounts attributable to NL stockholders:
Basic and diluted net income (loss) per share	$ (0.03)	$ (0.32)	$ 0.40	$ (0.90)
Weighted average shares used in the calculation of net income (loss) per share	48,756	48,727	48,741	48,721