Business segment information - Schedule of Business Segment Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Net sales:
Total net sales	$ 35,887	$ 36,616	$ 73,858	$ 77,767
Operating income (loss):
Total operating income	5,081	4,367	8,796	11,407
Interest income	1,295	992	2,519	1,939
Income before income taxes	6,376	5,359	11,315	13,346
Security Products
Net sales:
Total net sales	28,213	25,672	58,100	53,014
Marine Components
Net sales:
Total net sales	7,674	10,944	15,758	24,753
Operating Segments | Security Products
Operating income (loss):
Total operating income	5,442	4,134	10,892	9,513
Operating Segments | Marine Components
Operating income (loss):
Total operating income	1,387	1,943	1,421	5,260
Corporate
Operating income (loss):
Total operating income	$ (1,748)	$ (1,710)	$ (3,517)	$ (3,366)