CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Net sales	$ 33,730	$ 32,385	$ 64,907	$ 60,798
Cost of sales	22,791	21,151	44,344	40,061
Gross margin	10,939	11,234	20,563	20,737
Selling, general and administrative expense	5,317	5,251	10,650	10,380
Other operating income (expense):
Insurance recoveries	4,714	200	4,997	363
Other income, net	9	8	9	627
Litigation settlement expense, net	(19,571)	(62,000)	(19,571)	(62,000)
Corporate expense	(3,663)	(4,816)	(5,719)	(12,769)
Loss from operations	(12,889)	(60,625)	(10,371)	(63,422)
Equity in earnings of Kronos Worldwide, Inc.	8,944	23,645	18,169	45,124
Other income (expense):
Marketable equity securities	9,486	(18,685)	14,948	(20,266)
Other components of net periodic pension and OPEB cost	(428)	(99)	(856)	(198)
Interest and dividend income	2,123	1,222	3,642	2,294
Interest expense	(9)	(8)	(18)	(16)
Income (loss) before income taxes	7,227	(54,550)	25,514	(36,484)
Income tax expense (benefit)	667	(12,588)	3,228	(9,258)
Net income (loss)	6,560	(41,962)	22,286	(27,226)
Noncontrolling interest in net income of subsidiary	682	653	1,204	1,140
Net income (loss) attributable to NL stockholders	$ 5,878	$ (42,615)	$ 21,082	$ (28,366)
Amounts attributable to NL stockholders:
Basic and diluted net income (loss) per share	$ 0.12	$ (0.87)	$ 0.43	$ (0.58)
Weighted average shares used in the calculation of net income (loss) per share	48,740	48,721	48,734	48,718