CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Statement [Abstract]
Net sales	$ 26,505	$ 26,473	$ 83,314	$ 79,102
Cost of sales	18,387	18,331	57,471	54,598
Gross margin	8,118	8,142	25,843	24,504
Selling, general and administrative expense	4,684	4,710	14,402	13,872
Other operating income (expense):
Insurance recoveries	113	8,843	3,480	10,041
Other income	74	9	91	140
Corporate expense	(2,659)	(4,304)	(12,146)	(17,582)
Income from operations	962	7,980	2,866	3,231
Equity in earnings (losses) of Kronos Worldwide, Inc.	(3,600)	9,689	(46,584)	24,101
Other income - interest and dividend income	294	311	878	1,333
Income (loss) before income taxes	(2,344)	17,980	(42,840)	28,665
Income tax expense (benefit)	(3,581)	3,800	(25,534)	4,645
Net income (loss)	1,237	14,180	(17,306)	24,020
Noncontrolling interest in net income of subsidiary	294	291	976	904
Net income (loss) attributable to NL stockholders	$ 943	$ 13,889	$ (18,282)	$ 23,116
Amounts attributable to NL stockholders:
Basic and diluted net income (loss) per share	$ 0.02	$ 0.29	$ (0.38)	$ 0.47
Weighted average shares used in the calculation of net income (loss) per share	48,692	48,683	48,687	48,678