CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Net sales	$ 31,176	$ 28,413
Cost of sales	21,552	18,910
Gross margin	9,624	9,503
Selling, general and administrative expense	5,334	5,130
Other operating income (expense):
Insurance recoveries	283	163
Other income, net		619
Corporate expense	(2,055)	(7,953)
Income (loss) from operations	2,518	(2,798)
Equity in earnings of Kronos Worldwide, Inc.	9,225	21,479
Other income (expense):
Marketable equity securities	5,462	(1,581)
Other components of net periodic pension and OPEB cost	(428)	(99)
Interest and dividend income	1,519	1,072
Interest expense	(9)	(8)
Income before income taxes	18,287	18,065
Income tax expense	2,561	3,330
Net income	15,726	14,735
Noncontrolling interest in net income of subsidiary	522	487
Net income attributable to NL stockholders	$ 15,204	$ 14,248
Amounts attributable to NL stockholders:
Basic and diluted net income per share	$ 0.31	$ 0.29
Weighted average shares used in the calculation of net income per share	48,727	48,715