CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Net sales	$ 23,800	$ 33,730	$ 56,111	$ 64,907
Cost of sales	16,434	22,791	38,314	44,344
Gross margin	7,366	10,939	17,797	20,563
Selling, general and administrative expense	4,997	5,317	10,408	10,650
Other operating income (expense):
Insurance recoveries	86	4,714	108	4,997
Litigation settlement expense, net		(19,571)		(19,571)
Corporate expense	(2,441)	(3,654)	(4,949)	(5,710)
Income (loss) from operations	14	(12,889)	2,548	(10,371)
Equity in earnings of Kronos Worldwide, Inc.	5,651	8,944	13,858	18,169
Other income (expense):
Interest and dividend income	501	2,123	1,632	3,642
Marketable equity securities	(2,252)	9,486	(14,325)	14,948
Other components of net periodic pension and OPEB cost	(208)	(428)	(416)	(856)
Interest expense	(350)	(9)	(702)	(18)
Income before income taxes	3,356	7,227	2,595	25,514
Income tax expense (benefit)	(1,516)	667	(4,779)	3,228
Net income	4,872	6,560	7,374	22,286
Noncontrolling interest in net income of subsidiary	283	682	875	1,204
Net income attributable to NL stockholders	$ 4,589	$ 5,878	$ 6,499	$ 21,082
Amounts attributable to NL stockholders:
Basic and diluted net income per share	$ 0.09	$ 0.12	$ 0.13	$ 0.43
Weighted average shares used in the calculation of net income per share	48,771	48,740	48,763	48,734