Fair value measurement - Assets measured at fair value on nonrecurring basis (Details) - Nonrecurring - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	$ 1,629	$ 4,891
Loans held-for-sales		55,150
Other real estate owned	2,330	1,432
Other foreclosed assets	15
Total assets measured at fair value on non-recurring basis	3,974	61,473
Loans - write-down	(3)	(180)
Loans held-for-sale - write-down		(675)
Other real estate owned - write down	(628)	(495)
Other foreclosed assets - write down	(4)
Total assets measured - write down	(635)	(1,350)
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	0	0
Loans held-for-sales		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
Loans held-for-sales		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	1,629	4,891
Loans held-for-sales		55,150
Other real estate owned	2,330	1,432
Other foreclosed assets	15
Total assets measured at fair value on non-recurring basis	$ 3,974	$ 61,473