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, 2019	$ 327,213	$ 6,094	$ 299,102	$ 251,000	$ (251,690)	$ 22,707
Net income	11,498			10,371		1,127
Other comprehensive income (loss), net of tax	(400)				(400)
Issuance of NL common stock	100	4	96
Dividends paid	(5,853)			(5,853)
Dividends paid to noncontrolling interest	(507)					(507)
Ending Balance at Sep. 30, 2020	331,964	6,098	299,093	255,518	(252,090)	23,345
Other, net	(87)		(105)			18
Beginning Balance at Jun. 30, 2020	326,529	6,098	299,093	253,597	(255,521)	23,262
Net income	4,124			3,872		252
Other comprehensive income (loss), net of tax	3,431				3,431
Dividends paid	(1,951)			(1,951)
Dividends paid to noncontrolling interest	(169)					(169)
Ending Balance at Sep. 30, 2020	331,964	6,098	299,093	255,518	(252,090)	23,345
Beginning Balance at Dec. 31, 2020	335,349	6,098	299,093	257,875	(251,189)	23,472
Net income	38,029			36,267		1,762
Other comprehensive income (loss), net of tax	2,316				2,316
Issuance of NL common stock	101	2	99
Dividends paid	(8,783)			(8,783)
Dividends paid to noncontrolling interest	(999)					(999)
Ending Balance at Sep. 30, 2021	365,384	6,100	300,309	285,359	(248,873)	22,489
Other, net	(629)		1,117			(1,746)
Beginning Balance at Jun. 30, 2021	358,575	6,100	300,309	277,974	(248,082)	22,274
Net income	10,858			10,313		545
Other comprehensive income (loss), net of tax	(791)				(791)
Dividends paid	(2,928)			(2,928)
Dividends paid to noncontrolling interest	(330)					(330)
Ending Balance at Sep. 30, 2021	$ 365,384	$ 6,100	$ 300,309	$ 285,359	$ (248,873)	$ 22,489