| Fair Value, by Balance Sheet Grouping [Table Text Block] |
| | | Level in | | June 30, 2026 | | | December 31, 2025 | |
| | | Fair | | | | | | | | | | | | | | | | |
| | | Value | | Carrying | | | Fair | | | Carrying | | | Fair | |
| (Dollars in thousands) | | Hierarchy | | Values | | | Values | | | Values | | | Values | |
| Financial assets: | | | | | | | | | | | | | | | | | | | |
| Cash and cash equivalents | | Level 1 | | $ | 340,931 | | | $ | 340,931 | | | $ | 473,324 | | | $ | 473,324 | |
| Securities available for sale | | (1) | | | 1,125,529 | | | | 1,125,529 | | | | 1,102,230 | | | | 1,102,230 | |
| FHLBI stock | | (2) | | | 22,099 | | | | 22,099 | | | | 22,099 | | | | 22,099 | |
| Loans, net | | Level 3 | | | 4,860,112 | | | | 4,898,266 | | | | 4,763,697 | | | | 4,830,844 | |
| Mortgage loans held for sale | | Level 2 | | | 31,272 | | | | 31,783 | | | | 17,160 | | | | 17,319 | |
| Accrued interest receivable | | Level 2 | | | 23,685 | | | | 23,685 | | | | 23,638 | | | | 23,638 | |
| Interest rate swaps | | Level 2 | | | 16,923 | | | | 16,923 | | | | 23,212 | | | | 23,212 | |
| | | | | | | | | | | | | | | | | | | | |
| Financial liabilities: | | | | | | | | | | | | | | | | | | | |
| Deposits | | Level 2 | | | 5,296,388 | | | | 4,634,787 | | | | 5,284,452 | | | | 5,024,489 | |
| Securities sold under agreements to repurchase | | Level 2 | | | 217,470 | | | | 217,470 | | | | 232,291 | | | | 232,291 | |
| FHLBI advances | | Level 2 | | | 305,322 | | | | 297,864 | | | | 326,221 | | | | 321,069 | |
| Subordinated debentures | | Level 2 | | | 51,358 | | | | 58,076 | | | | 51,015 | | | | 51,019 | |
| Subordinated notes | | Level 2 | | | 89,829 | | | | 87,813 | | | | 89,657 | | | | 86,826 | |
| Term note | | Level 2 | | | 25,000 | | | | 25,000 | | | | 30,000 | | | | 30,000 | |
| Accrued interest payable | | Level 2 | | | 7,208 | | | | 7,208 | | | | 9,921 | | | | 9,921 | |
| Interest rate swaps | | Level 2 | | | 17,126 | | | | 17,126 | | | | 23,532 | | | | 23,532 | |
|