Investment securities available for sale - Additional Information (Details)	3 Months Ended
Mar. 31, 2024 USD ($) item	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)
Investment securities available for sale
Pledged Financial Instruments, Not Separately Reported, Securities for Federal Home Loan Bank	$ 575,000		$ 24,926,000
Amortized Cost	90,866,000		112,678,000
Proceeds from the sale of available-for-sale securities	$ 0	$ 0
Number of positions, Total months \| item	60
Total Fair Value	$ 53,624,000		66,969,000
Total Unrealized Losses	$ 8,372,000		$ 7,766,000

Amount, after allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), investment in debt security measured at amortized cost (held-to-maturity), and investment in debt security measured at fair value with change in fair value recognized in net income (trading).

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Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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