CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Net sales	$ 32,385	$ 30,002	$ 60,798	$ 59,950
Cost of sales	21,151	20,494	40,061	40,757
Gross margin	11,234	9,508	20,737	19,193
Selling, general and administrative expense	5,251	4,907	10,380	10,066
Other operating income (expense):
Insurance recoveries	200	66	363	116
Other income, net	8		627
Litigation settlement expense, net	(62,000)		(62,000)
Corporate expense	(4,816)	(3,233)	(12,769)	(8,555)
Income (loss) from operations	(60,625)	1,434	(63,422)	688
Equity in earnings of Kronos Worldwide, Inc.	23,645	59,745	45,124	70,920
Other income (expense):
Marketable equity securities	(18,685)		(20,266)
Other components of net periodic pension and OPEB cost	(99)	(177)	(198)	(354)
Interest and dividend income	1,222	881	2,294	1,577
Interest expense	(8)	(7)	(16)	(14)
Income (loss) before income taxes	(54,550)	61,876	(36,484)	72,817
Income tax expense (benefit)	(12,588)	20,278	(9,258)	22,457
Net income (loss)	(41,962)	41,598	(27,226)	50,360
Noncontrolling interest in net income of subsidiary	653	431	1,140	843
Net income (loss) attributable to NL stockholders	$ (42,615)	$ 41,167	$ (28,366)	$ 49,517
Amounts attributable to NL stockholders:
Basic and diluted net income (loss) per share	$ (0.87)	$ 0.85	$ (0.58)	$ 1.02
Weighted average shares used in the calculation of net income per share	48,721	48,710	48,718	48,708