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Investment securities (Tables) | 12 Months Ended
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Dec. 31, 2025
Investments, Debt and Equity Securities [Abstract] |
Unrealized Gain (Loss) on Investments [Table Text Block] | The following tables show the amortized cost, gross unrealized gains and losses and fair value of securities available for sale, by security type as of December 31, 2025 and 2024.
| 2025
| Amortized Cost |  | Gross Unrealized Gains |  | Gross Unrealized Losses |  | Fair Value
Securities available for sale: |  |  |  |  |  |  |
State and political subdivisions | $ | 198,083 |  |  | $ | 1 |  |  | $ | (34,820) |  |  | $ | 163,264 |
Collateralized mortgage obligations (1) | 234,217 |  |  | — |  |  | (40,534) |  |  | 193,683 |
Mortgage-backed securities (1) | 113,358 |  |  | — |  |  | (17,216) |  |  | 96,142 |
Collateralized loan obligations | 2,307 |  |  | 1 |  |  | (1) |  |  | 2,307 |
Corporate notes | 13,750 |  |  | — |  |  | (699) |  |  | 13,051 |
| $ | 561,715 |  |  | $ | 2 |  |  | $ | (93,270) |  |  | $ | 468,447 |
| 2024
| Amortized Cost |  | Gross Unrealized Gains |  | Gross Unrealized Losses |  | Fair Value
Securities available for sale: |  |  |  |  |  |  |
State and political subdivisions | $ | 215,942 |  |  | $ | — |  |  | $ | (41,797) |  |  | $ | 174,145 |
Collateralized mortgage obligations (1) | 278,754 |  |  | — |  |  | (59,490) |  |  | 219,264 |
Mortgage-backed securities (1) | 145,992 |  |  | — |  |  | (26,173) |  |  | 119,819 |
Collateralized loan obligations | 18,932 |  |  | 33 |  |  | — |  |  | 18,965 |
Corporate notes | 13,750 |  |  | — |  |  | (1,378) |  |  | 12,372 |
| $ | 673,370 |  |  | $ | 33 |  |  | $ | (128,838) |  |  | $ | 544,565 |
(1)Collateralized mortgage obligations and mortgage-backed securities consist of residential and commercial mortgage pass-through securities and collateralized mortgage obligations guaranteed by FNMA, FHLMC, GNMA and SBA.
Investments Classified by Contractual Maturity Date [Table Text Block] | The amortized cost and fair value of securities available for sale as of December 31, 2025, by contractual maturity, are shown below. Certain securities have call features that allow the issuer to call the securities prior to maturity. Expected maturities may differ from contractual maturities for collateralized mortgage obligations and mortgage-backed securities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Therefore, collateralized mortgage obligations and mortgage-backed securities are not included in the maturity categories within the following maturity summary.
| 2025
| Amortized Cost |  | Fair Value
Due after five years through ten years | $ | 30,902 |  |  | $ | 28,227 |
Due after ten years | 183,238 |  |  | 150,395 |
| 214,140 |  |  | 178,622 |
Collateralized mortgage obligations and mortgage-backed securities | 347,575 |  |  | 289,825 |
| $ | 561,715 |  |  | $ | 468,447 |
Schedule of Realized Gain (Loss) [Table Text Block] | The details of the sales of securities available for sale for the years ended December 31, 2025, 2024 and 2023 are summarized in the following table.
| 2025 |  | 2024 |  | 2023
Proceeds from sales | $ | 63,690 |  |  | $ | 11,841 |  |  | $ | 11,285 |
Gross gains on sales | 3 |  |  | — |  |  | — |
Gross losses on sales | 3,962 |  |  | 1,172 |  |  | 431 |
Schedule of Unrealized Loss on Investments [Table Text Block] | The following tables show the fair value and gross unrealized losses, aggregated by investment type and length of time that individual securities have been in a continuous loss position, as of December 31, 2025 and 2024.
|  | 2025
|  | Less than 12 months |  | 12 months or longer |  | Total
|  | Fair Value |  | Gross Unrealized Losses |  | No. of Securities |  | Fair Value |  | Gross Unrealized Losses |  | No. of Securities |  | Fair Value |  | Gross Unrealized Losses
Securities available for sale: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
State and political subdivisions |  | $ | — |  |  | $ | — |  |  | — |  |  | $ | 163,173 |  |  | $ | (34,820) |  |  | 68 |  |  | $ | 163,173 |  |  | $ | (34,820) |
Collateralized mortgage obligations |  | — |  |  | — |  |  | — |  |  | 193,683 |  |  | (40,534) |  |  | 53 |  |  | 193,683 |  |  | (40,534) |
Mortgage-backed securities |  | — |  |  | — |  |  | — |  |  | 96,142 |  |  | (17,216) |  |  | 22 |  |  | 96,142 |  |  | (17,216) |
Collateralized loan obligations |  | 1,110 |  |  | (1) |  |  | 1 |  |  | — |  |  | — |  |  | — |  |  | 1,110 |  |  | (1) |
Corporate notes |  | — |  |  | — |  |  | — |  |  | 13,052 |  |  | (699) |  |  | 8 |  |  | 13,052 |  |  | (699) |
|  | $ | 1,110 |  |  | $ | (1) |  |  | 1 |  | $ | 466,050 |  |  | $ | (93,269) |  |  | 151 |  | $ | 467,160 |  |  | $ | (93,270) |
|  | 2024
|  | Less than 12 months |  | 12 months or longer |  | Total
|  | Fair Value |  | Gross Unrealized Losses |  | No. of Securities |  | Fair Value |  | Gross Unrealized Losses |  | No. of Securities |  | Fair Value |  | Gross Unrealized Losses
Securities available for sale: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
State and political subdivisions |  | $ | 4,485 |  |  | $ | (271) |  |  | 7 |  | $ | 169,650 |  |  | $ | (41,526) |  |  | 90 |  | $ | 174,135 |  |  | $ | (41,797) |
Collateralized mortgage obligations |  | — |  |  | — |  |  | — |  |  | 219,264 |  |  | (59,490) |  |  | 69 |  | 219,264 |  |  | (59,490) |
Mortgage-backed securities |  | 610 |  |  | (3) |  |  | 1 |  | 119,209 |  |  | (26,170) |  |  | 25 |  | 119,819 |  |  | (26,173) |
Corporate notes |  | — |  |  | — |  |  | — |  |  | 12,372 |  |  | (1,378) |  |  | 8 |  | 12,372 |  |  | (1,378) |
|  | $ | 5,095 |  |  | $ | (274) |  |  | 8 |  | $ | 520,495 |  |  | $ | (128,564) |  |  | 192 |  | $ | 525,590 |  |  | $ | (128,838) |

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