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Long-term borrowings (Details Textual) - USD ($) |  |  |  | 1 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | ---
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% |  |  |  |  |  |  |

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