CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Net sales	$ 124,243	$ 118,217	$ 112,035
Cost of sales	85,280	79,946	77,210
Gross margin	38,963	38,271	34,825
Selling, general and administrative expense	21,297	20,460	19,587
Other operating income (expense):
Insurance recoveries	5,138	1,298	375
Other income, net	7,444	644	170
Litigation settlement expense, net	(19,266)	(62,000)
Corporate expense	(12,591)	(18,419)	(14,084)
Income (loss) from operations	(1,609)	(60,666)	1,699
Equity in earnings of Kronos Worldwide, Inc.	26,470	62,316	107,785
Other income (expense):
Interest and dividend income	6,672	5,069	3,570
Marketable equity securities	(863)	(60,941)
Other components of net periodic pension cost	(1,375)	(115)	(832)
Interest expense	(681)	(37)	(30)
Income (loss) before income taxes	28,614	(54,374)	112,192
Income tax expense (benefit)	579	(15,361)	(5,634)
Net income (loss)	28,035	(39,013)	117,826
Noncontrolling interest in net income of subsidiary	2,191	2,004	1,726
Net income (loss) attributable to NL stockholders	$ 25,844	$ (41,017)	$ 116,100
Amounts attributable to NL stockholders:
Basic and diluted net income (loss) per share	$ 0.53	$ (0.84)	$ 2.38
Weighted average shares used in the calculation of net income (loss) per share	48,745	48,727	48,711