CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Statement [Abstract]
Net sales	$ 28,404	$ 26,505	$ 82,586	$ 83,314
Cost of sales	19,005	18,387	56,496	57,471
Gross margin	9,399	8,118	26,090	25,843
Selling, general and administrative expense	4,926	4,684	14,547	14,402
Other operating income (expense):
Insurance recoveries	76	113	399	3,480
Other income		74	5	91
Corporate expense	(4,555)	(2,659)	(13,538)	(12,146)
Income (loss) from operations	(6)	962	(1,591)	2,866
Equity in earnings (losses) of Kronos Worldwide, Inc.	6,776	(3,600)	6,123	(46,584)
Other income - interest and dividend income	430	294	1,160	878
Income (loss) before income taxes	7,200	(2,344)	5,692	(42,840)
Income tax benefit	(560)	(3,581)	(1,052)	(25,534)
Net income (loss)	7,760	1,237	6,744	(17,306)
Noncontrolling interest in net income of subsidiary	388	294	996	976
Net income (loss) attributable to NL stockholders	$ 7,372	$ 943	$ 5,748	$ (18,282)
Amounts attributable to NL stockholders:
Basic and diluted net income (loss) per share	$ 0.15	$ 0.02	$ 0.12	$ (0.38)
Weighted average shares used in the calculation of net income (loss) per share	48,706	48,692	48,699	48,687