Investment securities available for sale - Additional Information (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2024 USD ($) item	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) item	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Debt securities	$ 0		$ 0		$ 24,926,000
Proceeds from the sale of available-for-sale securities	0		0	$ 50,079,000
Amortized Cost	$ 89,063,000		$ 89,063,000		112,678,000
Number of positions, total months | item	52		52
Total fair value	$ 43,999,000		$ 43,999,000		66,969,000
Total unrealized losses	$ 6,242,000		$ 6,242,000		$ 7,766,000
Weighted average yield		5.48%		5.48%
Loss on sale of investment securities, net		$ (4,986,000)		$ (4,986,000)
Duration of reinvested proceeds				3 years 4 months 25 days
Weighted average life of reinvested proceeds				5 years
Available-for-sale securities, securities sold
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		$ 55,195,000		$ 55,195,000
Weighted average yield		1.48%		1.48%
Loss on sale of investment securities, net				$ 4,986,000
Reduction of FHLB borrowings				$ 15,000,000.0
FLBH Borrowings rate		5.57%		5.57%