CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Net sales	$ 30,029	$ 26,993	$ 90,827	$ 86,943
Cost of sales	20,433	18,795	60,494	59,552
Gross margin	9,596	8,198	30,333	27,391
Selling, general and administrative expense	5,075	4,829	15,455	14,895
Other operating income (expense):
Insurance recoveries	526	103	889	219
Other income, net	18	140	645	140
Litigation settlement expense, net			(62,000)
Corporate expense	(1,583)	(2,575)	(14,352)	(11,130)
Income (loss) from operations	3,482	1,037	(59,940)	1,725
Equity in earnings of Kronos Worldwide, Inc.	9,905	22,437	55,029	93,357
Other income (expense):
Marketable equity securities	(35,645)		(55,911)
Other components of net periodic pension and OPEB cost	(99)	(177)	(297)	(531)
Interest and dividend income	1,336	977	3,630	2,554
Interest expense	(9)	(8)	(25)	(22)
Income (loss) before income taxes	(21,030)	24,266	(57,514)	97,083
Income tax expense (benefit)	(6,158)	6,466	(15,416)	28,923
Net income (loss)	(14,872)	17,800	(42,098)	68,160
Noncontrolling interest in net income of subsidiary	514	328	1,654	1,171
Net income (loss) attributable to NL stockholders	$ (15,386)	$ 17,472	$ (43,752)	$ 66,989
Amounts attributable to NL stockholders:
Basic and diluted net income (loss) per share	$ (0.32)	$ 0.36	$ (0.90)	$ 1.38
Weighted average shares used in the calculation of net income per share	48,727	48,715	48,721	48,710