CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income (loss)	$ 117,826	$ 16,693	$ (22,716)
Other comprehensive income (loss), net of tax:
Marketable securities	25,596	20,278	(46,917)
Currency translation	11,392	(3,475)	(18,211)
Interest rate swap	390	55	(445)
Total other comprehensive income (loss), net	41,109	12,512	(63,319)
Comprehensive income (loss)	158,935	29,205	(86,035)
Comprehensive income attributable to noncontrolling interest	1,726	1,368	1,193
Comprehensive income (loss) attributable to NL stockholders	157,209	27,837	(87,228)
Defined Benefit Pension Plans
Other comprehensive income (loss), net of tax:
Defined benefit pension plans/ Other postretirement benefit plans	3,759	(3,998)	2,548
OPEB
Other comprehensive income (loss), net of tax:
Defined benefit pension plans/ Other postretirement benefit plans	$ (28)	$ (348)	$ (294)