CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Net sales	$ 26,993	$ 28,404	$ 86,943	$ 82,586
Cost of sales	18,795	19,005	59,552	56,496
Gross margin	8,198	9,399	27,391	26,090
Selling, general and administrative expense	4,829	4,926	14,895	14,547
Other operating income (expense):
Insurance recoveries	103	76	219	399
Other income, net	137		140	5
Corporate expense	(2,749)	(4,555)	(11,661)	(13,538)
Income (loss) from operations	860	(6)	1,194	(1,591)
Equity in earnings of Kronos Worldwide, Inc.	22,437	6,776	93,357	6,123
Other income (expense):
Interest and dividend income	977	430	2,554	1,160
Interest expense	(8)		(22)
Income before income taxes	24,266	7,200	97,083	5,692
Income tax expense (benefit)	6,466	(560)	28,923	(1,052)
Net income	17,800	7,760	68,160	6,744
Noncontrolling interest in net income of subsidiary	328	388	1,171	996
Net income attributable to NL stockholders	$ 17,472	$ 7,372	$ 66,989	$ 5,748
Amounts attributable to NL stockholders:
Basic and diluted net income per share	$ 0.36	$ 0.15	$ 1.38	$ 0.12
Weighted average shares used in the calculation of net income per share	48,715	48,706	48,710	48,699