Provision for income taxes - Provision for income taxes (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Income tax expense:
Deferred income tax benefit			$ (370)	$ (421)
Total provision for income taxes	$ 1,532	$ 1,287	2,717	3,206
Expected tax expense, at the U.S. federal statutory income tax rate of 21%	1,339	1,126	$ 2,376	$ 2,803
U.S. federal statutory income tax rate			21.00%	21.00%
State income taxes	188	161	$ 333	$ 401
Other, net	5		8	2
Total provision for income taxes	1,532	1,287	2,717	3,206
Disclosure Other Comprehensive Income Loss Tax Effects Allocation to Component Of Other Comprehensive Income Loss [Abstract]
Other comprehensive loss - marketable securities	1	(18)		(31)
Total	$ 1,533	$ 1,269	$ 2,717	$ 3,175