CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Net sales	$ 32,311	$ 31,176
Cost of sales	21,880	21,552
Gross margin	10,431	9,624
Selling, general and administrative expense	5,411	5,334
Other operating income (expense):
Insurance recoveries	22	283
Corporate expense	(2,508)	(2,055)
Income from operations	2,534	2,518
Equity in earnings of Kronos Worldwide, Inc.	8,207	9,225
Other income (expense):
Interest and dividend income	1,131	1,519
Marketable equity securities	(12,073)	5,462
Other components of net periodic pension and OPEB cost	(208)	(428)
Interest expense	(352)	(9)
Income (loss) before income taxes	(761)	18,287
Income tax expense (benefit)	(3,263)	2,561
Net income	2,502	15,726
Noncontrolling interest in net income of subsidiary	592	522
Net income attributable to NL stockholders	$ 1,910	$ 15,204
Amounts attributable to NL stockholders:
Basic and diluted net income per share	$ 0.04	$ 0.31
Weighted average shares used in the calculation of net income per share	48,756	48,727