Loans and allowance for credit losses - Provision for credit losses (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Provision for Loan, Lease, and Other Losses [Abstract]
Provision (recovery) for loans	$ (53,000)	$ 100,000	$ (52,000)	$ (300,000)
Provision (recovery) for unfunded commitments	$ 53,000		$ 52,000
Total		$ 100,000		$ (300,000)