Marketable securities - Schedule of Marketable Securities (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Marketable Securities [Line Items]
Market value, Current assets	$ 80,217	$ 70,164
Market value, Noncurrent assets	15,882	26,350
Level 1 | Valhi Inc | Common stock
Marketable Securities [Line Items]
Market value, Noncurrent assets	15,882	26,350
Cost or amortized cost, Noncurrent assets	24,347	24,347
Unrealized gain (loss), Noncurrent assets	(8,465)	2,003
Level 2 | Fixed income securities
Marketable Securities [Line Items]
Market value, Current assets	80,217	70,164
Cost or amortized cost, Current assets	80,425	70,226
Unrealized gain (loss), Current assets	$ (208)	$ (62)