CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Income Statement [Abstract]
Net sales	$ 42,050	$ 35,924
Cost of sales	29,970	24,889
Gross margin	12,080	11,035
Selling, general and administrative expense	5,774	5,218
Other operating income (expense):
Corporate expense	(2,436)	(1,845)
Income from operations	3,870	3,972
Equity in earnings of Kronos Worldwide, Inc.	17,533	5,968
Other income (expense):
Interest and dividend income	309	440
Marketable equity securities	671	6,360
Other components of net periodic pension and OPEB cost	(223)	(71)
Interest expense	(246)	(298)
Income before income taxes	21,914	16,371
Income tax expense	2,705	2,505
Net income	19,209	13,866
Noncontrolling interest in net income of subsidiary	652	609
Net income attributable to NL stockholders	$ 18,557	$ 13,257
Amounts attributable to NL stockholders:
Net income per basic share	$ 0.38	$ 0.27
Net income per diluted share	$ 0.38	$ 0.27
Weighted average shares outstanding - basic	48,803	48,789
Weighted average shares outstanding - diluted	48,803	48,789