Fair value measurement - Assets measured at fair value on nonrecurring basis (Details) - Nonrecurring - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	$ 18,923	$ 6,694
Other real estate owned	2,815	2,161
Other foreclosed assets	41
Total assets measured at fair value on non-recurring basis	21,779	8,855
Loans - write-down	(7,092)	(1,183)
Other real estate owned - write down	(656)	(769)
Other foreclosed assets - write down	(9)
Total assets measured - write down	(7,757)	(1,952)
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
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
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	18,923	6,694
Other real estate owned	2,815	2,161
Other foreclosed assets	41
Total assets measured at fair value on non-recurring basis	$ 21,779	$ 8,855