CONDENSED CONSOLIDATED STATEMENTS OF 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, 2018	$ 303,558	$ 6,090	$ 301,139	$ 225,156	$ (248,270)	$ 19,443
Net income	22,286			21,082		1,204
Other comprehensive income (loss), net of tax	3,205				3,205
Issuance of NL common stock	100	4	96
Dividends paid to noncontrolling interest	(235)					(235)
Equity transactions with controlling interest, net and other	(288)		(1,831)			1,543
Ending Balance at Jun. 30, 2019	328,626	6,094	299,404	246,238	(245,065)	21,955
Beginning Balance at Mar. 31, 2019	319,900	6,090	301,139	240,360	(247,537)	19,848
Net income	6,560			5,878		682
Other comprehensive income (loss), net of tax	2,472				2,472
Issuance of NL common stock	100	4	96
Dividends paid to noncontrolling interest	(118)					(118)
Equity transactions with controlling interest, net and other	(288)		(1,831)			1,543
Ending Balance at Jun. 30, 2019	328,626	6,094	299,404	246,238	(245,065)	21,955
Beginning Balance at Dec. 31, 2019	327,213	6,094	299,102	251,000	(251,690)	22,707
Net income	7,374			6,499		875
Other comprehensive income (loss), net of tax	(3,831)				(3,831)
Issuance of NL common stock	100	4	96
Dividends paid	(3,902)			(3,902)
Dividends paid to noncontrolling interest	(338)					(338)
Other, net	(87)		(105)			18
Ending Balance at Jun. 30, 2020	326,529	6,098	299,093	253,597	(255,521)	23,262
Beginning Balance at Mar. 31, 2020	318,205	6,094	298,865	250,960	(260,845)	23,131
Net income	4,872			4,589		283
Other comprehensive income (loss), net of tax	5,324				5,324
Issuance of NL common stock	100	4	96
Dividends paid	(1,952)			(1,952)
Dividends paid to noncontrolling interest	(170)					(170)
Other, net	150		132			18
Ending Balance at Jun. 30, 2020	$ 326,529	$ 6,098	$ 299,093	$ 253,597	$ (255,521)	$ 23,262