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Long-term borrowings (Details Textual) - USD ($)				1 Months Ended		9 Months Ended
Long-term borrowings (Details Textual) - USD ($)	Nov. 01, 2021	Jan. 07, 2020	Dec. 31, 2015	Aug. 31, 2024	Nov. 30, 2021	Sep. 30, 2024	Sep. 30, 2023	Jun. 30, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Long-rem advances from FHLB						$ 0			$ 0
Residential mortgage, commercial real estate, and multi-family loans						1,700,000,000			$ 1,600,000,000
Additional borrowing limit						695,800,000
Outstanding subordinated notes						$ 2,535,000	$ 0
Subordinated Notes
Debt Instrument [Line Items]
Aggregate principal amount					$ 75,000,000
Maturity date					Dec. 15, 2031
Fixed rate					3.125%
Notes maturity term					5 years
Basis spread on variable rate					220.00%
Net proceeds from sale					$ 73,800,000
Outstanding subordinated notes				$ 3,000,000
Junior Subordinated Debt Securities \| Cortland Bank
Debt Instrument [Line Items]
Maturity date	Sep. 15, 2037
Business acquisition, date of merger agreement	Nov. 01, 2021
Acquisition-date fair value	$ 4,300,000
Interest rate, effective percentage								6.66%	7.10%
Junior Subordinated Debt Securities \| Maple Leaf
Debt Instrument [Line Items]
Maturity date		Dec. 15, 2036
Business acquisition, date of merger agreement		Jan. 07, 2020
Interest rate, effective percentage						7.01%			7.45%
Junior Subordinated Debt Securities \| National Bancshares Corporation
Debt Instrument [Line Items]
Maturity date			Jun. 15, 2035
Interest rate, effective percentage						6.91%			7.35%
Junior Subordinated Debt Securities \| 3 Month SOFR Rate \| Cortland Bank
Debt Instrument [Line Items]
Basis spread on variable rate	1.45%
Debt instrument, additional spread adjustment	0.26%
Junior Subordinated Debt Securities \| 3 Month SOFR Rate \| Maple Leaf
Debt Instrument [Line Items]
Basis spread on variable rate		1.70%
Debt instrument, additional spread adjustment		0.26%
Junior Subordinated Debt Securities \| 3 Month SOFR Rate \| National Bancshares Corporation
Debt Instrument [Line Items]
Basis spread on variable rate			1.80%
Debt instrument, additional spread adjustment		0.26%