Stockholders' equity - Schedule of Changes in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	$ 396,904
Balance at end of period	397,644
Currency Translation
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	(185,423)	$ (177,119)
Other comprehensive income (loss)	4,185	(4,966)
Balance at end of period	(181,238)	(182,085)
Accumulated Defined Benefit Plans Adjustment \| Defined Benefit Pension Plans
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	(36,666)	(41,373)
Other comprehensive income (loss)	317	379
Balance at end of period	(36,349)	(40,994)
Other \| OPEB plans
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	(1,267)	(1,114)
Other comprehensive income (loss)	(33)	(47)
Balance at end of period	(1,300)	(1,161)
Marketable debt securities
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	0	(15)
Other comprehensive income (loss)	0	15
Balance at end of period	0	0
Total accumulated other comprehensive loss
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	(223,356)	(219,621)
Other comprehensive income (loss)	4,469	(4,619)
Balance at end of period	$ (218,887)	$ (224,240)

NL INDUSTRIES INC 10-Q