CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Net sales	$ 30,002	$ 27,107	$ 59,950	$ 54,182
Cost of sales	20,494	18,621	40,757	37,491
Gross margin	9,508	8,486	19,193	16,691
Selling, general and administrative expense	4,907	4,769	10,066	9,621
Other operating income (expense):
Insurance recoveries	66	233	116	323
Corporate expense	(3,410)	(3,329)	(8,909)	(8,978)
Income (loss) from operations	1,257	621	334	(1,585)
Equity in earnings (losses) of Kronos Worldwide, Inc.	59,745	497	70,920	(653)
Other income (expense):
Interest and dividend income	881	377	1,577	730
Interest expense	(7)		(14)
Income (loss) before income taxes	61,876	1,495	72,817	(1,508)
Income tax expense (benefit)	20,278	330	22,457	(492)
Net income (loss)	41,598	1,165	50,360	(1,016)
Noncontrolling interest in net income of subsidiary	431	320	843	608
Net income (loss) attributable to NL stockholders	$ 41,167	$ 845	$ 49,517	$ (1,624)
Amounts attributable to NL stockholders:
Basic and diluted net income (loss) per share	$ 0.85	$ 0.02	$ 1.02	$ (0.03)
Weighted average shares used in the calculation of net income (loss) per share	48,710	48,699	48,708	48,695