CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net sales	$ 112,035	$ 108,920	$ 108,994
Cost of sales	77,210	73,753	75,593
Gross margin	34,825	35,167	33,401
Selling, general and administrative expense	19,587	19,593	19,430
Other operating income (expense):
Insurance recoveries	375	443	3,657
Other income, net	170	9	120
Corporate expense	(14,916)	(17,009)	(17,480)
Income (loss) from operations	867	(983)	268
Equity in earnings (losses) of Kronos Worldwide, Inc.	107,785	13,171	(52,770)
Other income (expense):
Securities transactions, net			3
Interest and dividends	3,570	1,732	1,172
Interest expense	(30)	(4)
Income (loss) before taxes	112,192	13,916	(51,327)
Income tax benefit	(5,634)	(2,777)	(28,611)
Net income (loss)	117,826	16,693	(22,716)
Noncontrolling interest in net income of subsidiary	1,726	1,368	1,193
Net income (loss) attributable to NL stockholders	$ 116,100	$ 15,325	$ (23,909)
Amounts attributable to NL stockholders:
Basic and diluted net income (loss) per share	$ 2.38	$ 0.31	$ (0.49)
Weighted average shares used in the calculation of net income (loss) per share	48,711	48,701	48,688