CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income (loss)	Noncontrolling interest in subsidiary
Beginning Balance at Dec. 31, 2016	$ 194,270	$ 6,088	$ 300,674	$ 104,004	$ (232,846)	$ 16,350
Net income (loss)	117,826			116,100		1,726
Other comprehensive income (loss), net of tax	41,109				41,109
Issuance of NL common stock	83	1	82
Dividends paid to noncontrolling interest	(333)					(333)
Other, net	123		110			13
Ending Balance at Dec. 31, 2017	353,078	6,089	300,866	220,104	(191,737)	17,756
Change in accounting principle-ASU 2016-01 at Dec. 31, 2017				46,069	(46,069)
Balance at January 1, 2018, as adjusted	353,078	6,089	300,866	266,173	(237,806)	17,756
Net income (loss)	(39,013)			(41,017)		2,004
Other comprehensive income (loss), net of tax	(10,464)				(10,464)
Issuance of NL common stock	120	1	119
Dividends paid to noncontrolling interest	(335)					(335)
Other, net	172		154			18
Ending Balance at Dec. 31, 2018	303,558	6,090	301,139	225,156	(248,270)	19,443
Net income (loss)	28,035			25,844		2,191
Other comprehensive income (loss), net of tax	(3,420)				(3,420)
Issuance of NL common stock	100	4	96
Dividends paid to noncontrolling interest	(470)					(470)
Other, net	(590)		(2,133)			1,543
Ending Balance at Dec. 31, 2019	$ 327,213	$ 6,094	$ 299,102	$ 251,000	$ (251,690)	$ 22,707