Income taxes - Provision for income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current:
Federal	$ 10,319	$ 11,995	$ 453
State and local	2,940	2,835	350
Total	13,259	14,830	803
Deferred:
Federal	3,667	(323)	267
State and local	647	(1,126)	70
Total	4,314	(1,449)	337
Expense for income taxes	$ 17,573	$ 13,381	$ 1,140