CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Net sales	$ 118,217	$ 112,035	$ 108,920
Cost of sales	79,946	77,210	73,753
Gross margin	38,271	34,825	35,167
Selling, general and administrative expense	20,460	19,587	19,593
Other operating income (expense):
Insurance recoveries	1,298	375	443
Other income, net	644	170	9
Litigation settlement expense, net	(62,000)
Corporate expense	(18,419)	(14,084)	(16,741)
Income (loss) from operations	(60,666)	1,699	(715)
Equity in earnings of Kronos Worldwide, Inc.	62,316	107,785	13,171
Other income (expense):
Marketable equity securities	(60,941)
Other components of net periodic pension cost	(115)	(832)	(268)
Interest and dividends	5,069	3,570	1,732
Interest expense	(37)	(30)	(4)
Income (loss) before taxes	(54,374)	112,192	13,916
Income tax benefit	(15,361)	(5,634)	(2,777)
Net income (loss)	(39,013)	117,826	16,693
Noncontrolling interest in net income of subsidiary	2,004	1,726	1,368
Net income (loss) attributable to NL stockholders	$ (41,017)	$ 116,100	$ 15,325
Amounts attributable to NL stockholders:
Basic and diluted net income (loss) per share	$ (0.84)	$ 2.38	$ 0.31
Weighted average shares used in the calculation of net income (loss) per share	48,727	48,711	48,701