| Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] |
| | | | | | | March 31, 2026 | |
| | | | | | | Fair Value Measurements at Reporting Date Using | |
| | | Total Fair Value | | | Quoted Prices in Active Markets for Identical Assets (Level 1) | | | Significant Other Observable Inputs (Level 2) | | | Significant Unobservable Inputs (Level 3) | |
| (dollars in thousands) | | | | | | | | | | | | | | | | |
| Recurring fair value measurements: Assets | | | | | | | | | | | | | | | | |
| Available-for-sale securities: | | | | | | | | | | | | | | | | |
| Federal agency obligations | | $ | 354,803 | | | $ | - | | | $ | 354,803 | | | $ | - | |
| Residential mortgage pass-through securities | | | 596,158 | | | | - | | | | 596,158 | | | | - | |
| Commercial mortgage pass-through securities | | | 26,628 | | | | - | | | | 26,628 | | | | - | |
| Obligations of U.S. states and political subdivisions | | | 204,563 | | | | - | | | | 198,185 | | | | 6,378 | |
| Corporate bonds and notes | | | 13,466 | | | | - | | | | 13,466 | | | | - | |
| Asset-backed securities | | | 506 | | | | - | | | | 506 | | | | - | |
| Other securities | | | 260 | | | | 260 | | | | - | | | | - | |
| Total available-for-sale securities | | | 1,196,384 | | | | 260 | | | | 1,189,746 | | | | 6,378 | |
| | | | | | | | | | | | | | | | | |
| Equity securities | | | 19,422 | | | | 10,010 | | | | 9,412 | | | | - | |
| Derivatives | | | 17,165 | | | | - | | | | 17,165 | | | | - | |
| Total assets | | $ | 1,232,971 | | | $ | 10,270 | | | $ | 1,216,323 | | | $ | 6,378 | |
| | | | | | | | | | | | | | | | | |
| Liabilities | | | | | | | | | | | | | | | | |
| Derivatives - interest rate contracts | | | 372 | | | | - | | | | 372 | | | | - | |
| Total liabilities | | $ | 372 | | | $ | - | | | $ | 372 | | | $ | - | |
| | | | | | | December 31, 2025 | |
| | | | | | | Fair Value Measurements at Reporting Date Using | |
| | | Total Fair Value | | | Quoted Prices in Active Markets for Identical Assets (Level 1) | | | Significant Other Observable Inputs (Level 2) | | | Significant Unobservable Inputs (Level 3) | |
| (dollars in thousands) | | | | | | | | | | | | | | | | |
| Recurring fair value measurements: Assets | | | | | | | | | | | | | | | | |
| Available-for-sale securities: | | | | | | | | | | | | | | | | |
| Federal agency obligations | | $ | 391,190 | | | $ | - | | | $ | 391,190 | | | $ | - | |
| Residential mortgage pass- through securities | | | 607,144 | | | | - | | | | 607,144 | | | | - | |
| Commercial mortgage pass-through securities | | | 26,969 | | | | - | | | | 26,969 | | | | - | |
| Obligations of U.S. states and political subdivisions | | | 212,409 | | | | - | | | | 205,897 | | | | 6,512 | |
| Corporate bonds and notes | | | 12,519 | | | | - | | | | 12,519 | | | | - | |
| Asset-backed securities | | | 525 | | | | - | | | | 525 | | | | - | |
| Other securities | | | 182 | | | | 182 | | | | - | | | | - | |
| Total available-for-sale securities | | $ | 1,250,938 | | | $ | 182 | | | $ | 1,244,244 | | | $ | 6,512 | |
| | | | | | | | | | | | | | | | | |
| Equity securities | | | 19,287 | | | | 10,073 | | | | 9,214 | | | | - | |
| Derivatives | | | 16,074 | | | | - | | | | 16,074 | | | | - | |
| Total assets | | $ | 1,286,299 | | | $ | 10,255 | | | $ | 1,269,532 | | | $ | 6,512 | |
| | | | | | | | | | | | | | | | | |
| Liabilities | | | | | | | | | | | | | | | | |
| Derivatives - interest rate contracts | | | 704 | | | | - | | | | 704 | | | | - | |
| Total liabilities | | $ | 704 | | | $ | - | | | $ | 704 | | | $ | - | |
|
| Fair Value, by Balance Sheet Grouping [Table Text Block] |
| | | | | | | | | | | Fair Value Measurements | |
| | | Carrying Amount | | | Fair Value | | | Quoted Prices in Active Markets for Identical Assets (Level 1) | | | Significant Other Observable Inputs (Level 2) | | | Significant Unobservable Inputs (Level 3) | |
| | | (dollars in thousands) | |
| | | | | | | | | | | | | | | | | | | | | |
| March 31, 2026 | | | | | | | | | | | | | | | | | | | | |
| Financial assets: | | | | | | | | | | | | | | | | | | | | |
| Cash and due from banks | | $ | 344,471 | | | $ | 344,471 | | | $ | 344,471 | | | $ | - | | | $ | - | |
| Available-for-sale securities: | | | 1,196,384 | | | | 1,196,384 | | | | 260 | | | | 1,189,746 | | | | 6,378 | |
| Restricted investments in bank stocks | | | 51,464 | | | | n/a | | | | n/a | | | | n/a | | | | n/a | |
| Equity securities | | | 19,422 | | | | 19,422 | | | | 10,010 | | | | 9,412 | | | | - | |
| Net loans | | | 11,582,540 | | | | 11,469,582 | | | | - | | | | - | | | | 11,469,582 | |
| Loans held-for-sale | | | 10,222 | | | | 10,222 | | | | - | | | | 10,222 | | | | - | |
| Derivatives - interest rate contracts | | | 17,165 | | | | 17,165 | | | | - | | | | 17,165 | | | | - | |
| Accrued interest receivable | | | 62,473 | | | | 62,473 | | | | - | | | | 4,918 | | | | 57,555 | |
| | | | | | | | | | | | | | | | | | | | | |
| Financial liabilities: | | | | | | | | | | | | | | | | | | | | |
| Noninterest-bearing deposits | | | 2,393,938 | | | | 2,393,938 | | | | 2,393,938 | | | | - | | | | - | |
| Interest-bearing deposits | | | 9,119,115 | | | | 9,111,328 | | | | 6,108,144 | | | | 3,003,184 | | | | - | |
| Borrowings | | | 827,477 | | | | 827,553 | | | | - | | | | 827,553 | | | | - | |
| Subordinated debentures | | | 202,050 | | | | 202,411 | | | | - | | | | 202,411 | | | | - | |
| Derivatives - interest rate contracts | | | 372 | | | | 372 | | | | - | | | | 372 | | | | - | |
| Accrued interest payable | | | 15,151 | | | | 15,151 | | | | - | | | | 15,151 | | | | - | |
| | | | | | | | | | | | | | | | | | | | | |
| December 31, 2025 | | | | | | | | | | | | | | | | | | | | |
| Financial assets: | | | | | | | | | | | | | | | | | | | | |
| Cash and due from banks | | $ | 380,895 | | | $ | 380,895 | | | $ | 380,895 | | | $ | - | | | $ | - | |
| Available-for-sale securities: | | | 1,250,938 | | | | 1,250,938 | | | | 182 | | | | 1,244,244 | | | | 6,512 | |
| Restricted investment in bank stocks | | | 54,722 | | | | n/a | | | | n/a | | | | n/a | | | | n/a | |
| Equity securities | | | 19,287 | | | | 19,287 | | | | 10,073 | | | | 9,214 | | | | - | |
| Net loans | | | 11,298,975 | | | | 11,232,658 | | | | - | | | | - | | | | 11,232,658 | |
| Derivatives - interest rate contracts | | | 16,074 | | | | 16,074 | | | | - | | | | 16,074 | | | | - | |
| Accrued interest receivable | | | 60,761 | | | | 60,761 | | | | - | | | | 5,172 | | | | 55,589 | |
| | | | | | | | | | | | | | | | | | | | | |
| Financial liabilities: | | | | | | | | | | | | | | | | | | | | |
| Noninterest-bearing deposits | | | 2,420,397 | | | | 2,420,397 | | | | 2,420,397 | | | | - | | | | - | |
| Interest-bearing deposits | | | 8,820,218 | | | | 8,816,234 | | | | 6,023,341 | | | | 2,792,893 | | | | - | |
| Borrowings | | | 903,489 | | | | 902,908 | | | | - | | | | 902,908 | | | | - | |
| Subordinated debentures | | | 201,864 | | | | 204,454 | | | | - | | | | 204,454 | | | | - | |
| Derivative - interest rate contracts | | | 704 | | | | 704 | | | | - | | | | 704 | | | | | |
| Accrued interest payable | | | 12,740 | | | | 12,740 | | | | - | | | | 12,740 | | | | - | |
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