Stockholders' equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Class Of Stock [Line Items]
Payments of dividends	$ 13.7	$ 13.7	$ 11.7
Special dividend declared and paid	$ 17.1
Special dividend declared and paid (per share)	$ 0.35
Quarterly dividends paid (in dollars per share)	$ 0.07	$ 0.07	$ 0.06
Kronos
Class Of Stock [Line Items]
Number of shares purchased in market transaction		2,000
NL
Class Of Stock [Line Items]
Common stock awarded to board of directors	17,750	15,000	13,750
Shares available for award	200,000
NL | Maximum
Class Of Stock [Line Items]
Aggregate of common stock awarded to directors			200,000
CompX
Class Of Stock [Line Items]
Number of shares available for purchase under repurchase authorizations	523,647
Shares available for award	124,450
CompX | Common Class A
Class Of Stock [Line Items]
Number of shares purchased in market transaction		78,900	75,000
Value of shares purchased in market transaction		$ 1.7	$ 1.3
CompX | Common Class A | Affiliates
Class Of Stock [Line Items]
Number of shares purchased in market transaction		8,900
CompX | Common Class A | Open Market Transaction
Class Of Stock [Line Items]
Number of shares purchased in market transaction		70,000
CompX | Maximum
Class Of Stock [Line Items]
Aggregate of common stock awarded to directors	200,000		200,000
Kronos
Class Of Stock [Line Items]
Shares available for award	97,100
Kronos | Maximum
Class Of Stock [Line Items]
Aggregate of common stock awarded to directors	200,000