CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net income (loss)	$ (14,872)	$ 17,800	$ (42,098)	$ 68,160
Other comprehensive income (loss), net of tax:
Marketable securities		(5,260)		(9,851)
Currency translation	1,103	5,908	(2,414)	10,604
Interest rate swap		362		390
Total other comprehensive income, net	1,997	1,699	299	2,996
Comprehensive income (loss)	(12,875)	19,499	(41,799)	71,156
Comprehensive income attributable to noncontrolling interest	514	328	1,654	1,171
Comprehensive income (loss) attributable to NL stockholders	(13,389)	19,171	(43,453)	69,985
Defined Benefit Pension Plans
Other comprehensive income (loss), net of tax:
Defined benefit pension plans/ Other postretirement benefit plans	959	738	2,916	1,998
OPEB
Other comprehensive income (loss), net of tax:
Defined benefit pension plans/ Other postretirement benefit plans	$ (65)	$ (49)	$ (203)	$ (145)