Fair value measurement - Assets measured at fair value on nonrecurring basis (Details) - Nonrecurring - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	$ 4,166	$ 9,113
Other real estate owned	5,749	5,457
Other foreclosed assets	174	44
Total assets measured at fair value on non-recurring basis	10,089	14,614
Loans - write-down	(654)	(3,087)
Other real estate owned - write down	(1,889)	(1,012)
Other foreclosed assets - write down	(38)	(14)
Total assets measured - write down	(2,581)	(4,113)
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	0	0
Other real estate owned	0	0
Other foreclosed assets	0	0
Total assets measured at fair value on non-recurring basis	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	0	0
Other real estate owned	0	0
Other foreclosed assets	0	0
Total assets measured at fair value on non-recurring basis	0	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	4,166	9,113
Other real estate owned	5,749	5,457
Other foreclosed assets	174	44
Total assets measured at fair value on non-recurring basis	$ 10,089	$ 14,614