| Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] |
| | | | | | | Quoted | | | | | | | | | |
| | | | | | | Prices in | | | | | | | | | |
| | | | | | | Active | | | | | | | | | |
| | | | | | | Markets | | | Significant | | | | | |
| | | | | | | for | | | Other | | | Significant | |
| | | | | | | Identical | | | Observable | | | Unobservable | |
| | | | | | | Assets | | | Inputs | | | Inputs | |
| (Dollars in thousands) | | Total | | | (Level 1) | | | (Level 2) | | | (Level 3) | |
| Available for sale securities | | | | | | | | | | | | | | | | |
| U.S. Government agency debt obligations | | $ | 547,409 | | | $ | 0 | | | $ | 547,409 | | | $ | 0 | |
| Mortgage-backed securities | | | 25,182 | | | | 0 | | | | 25,182 | | | | 0 | |
| Municipal general obligation bonds | | | 184,790 | | | | 0 | | | | 184,396 | | | | 394 | |
| Municipal revenue bonds | | | 29,702 | | | | 0 | | | | 29,702 | | | | 0 | |
| Other investments | | | 500 | | | | 0 | | | | 500 | | | | 0 | |
| Interest rate swaps | | | 24,722 | | | | 0 | | | | 24,722 | | | | 0 | |
| Total assets | | $ | 812,305 | | | $ | 0 | | | $ | 811,911 | | | $ | 394 | |
| | | | | | | | | | | | | | | | | |
| Interest rate swaps | | | 25,073 | | | | 0 | | | | 25,073 | | | | 0 | |
| Total liabilities | | $ | 25,073 | | | $ | 0 | | | $ | 25,073 | | | $ | 0 | |
| | | | | | | Quoted | | | | | | | | | |
| | | | | | | Prices in | | | | | | | | | |
| | | | | | | Active | | | | | | | | | |
| | | | | | | Markets | | | Significant | | | | | |
| | | | | | | for | | | Other | | | Significant | |
| | | | | | | Identical | | | Observable | | | Unobservable | |
| | | | | | | Assets | | | Inputs | | | Inputs | |
| (Dollars in thousands) | | Total | | | (Level 1) | | | (Level 2) | | | (Level 3) | |
| Available for sale securities | | | | | | | | | | | | | | | | |
| U.S. Government agency debt obligations | | $ | 495,581 | | | $ | 0 | | | $ | 495,581 | | | $ | 0 | |
| Mortgage-backed securities | | | 25,368 | | | | 0 | | | | 25,368 | | | | 0 | |
| Municipal general obligation bonds | | | 180,170 | | | | 0 | | | | 179,777 | | | | 393 | |
| Municipal revenue bonds | | | 28,733 | | | | 0 | | | | 28,733 | | | | 0 | |
| Other investments | | | 500 | | | | 0 | | | | 500 | | | | 0 | |
| Interest rate swaps | | | 26,793 | | | | 0 | | | | 26,793 | | | | 0 | |
| Total assets | | $ | 757,145 | | | $ | 0 | | | $ | 756,752 | | | $ | 393 | |
| | | | | | | | | | | | | | | | | |
| Interest rate swaps | | | 27,050 | | | | 0 | | | | 27,050 | | | | 0 | |
| Total liabilities | | $ | 27,050 | | | $ | 0 | | | $ | 27,050 | | | $ | 0 | |
|
| Fair Value, Assets and Liabilities Measured on Nonrecurring Basis, Valuation Techniques [Table Text Block] |
| | | | | | | Quoted | | | | | | | | | |
| | | | | | | Prices in | | | | | | | | | |
| | | | | | | Active | | | Significant | | | | | |
| | | | | | | Markets for | | | Other | | | Significant | |
| | | | | | | Identical | | | Observable | | | Unobservable | |
| | | | | | | Assets | | | Inputs | | | Inputs | |
| (Dollars in thousands) | | Total | | | (Level 1) | | | (Level 2) | | | (Level 3) | |
| | | | | | | | | | | | | | | | | |
| Collateral dependent loans | | $ | 1,642 | | | $ | 0 | | | $ | 0 | | | $ | 1,642 | |
| Total | | $ | 1,642 | | | $ | 0 | | | $ | 0 | | | $ | 1,642 | |
| | | | | | | Quoted | | | | | | | | | |
| | | | | | | Prices | | | | | | | | | |
| | | | | | | in Active | | | Significant | | | | | |
| | | | | | | Markets for | | | Other | | | Significant | |
| | | | | | | Identical | | | Observable | | | Unobservable | |
| | | | | | | Assets | | | Inputs | | | Inputs | |
| (Dollars in thousands) | | Total | | | (Level 1) | | | (Level 2) | | | (Level 3) | |
| | | | | | | | | | | | | | | | | |
| Collateral dependent loans | | $ | 2,173 | | | $ | 0 | | | $ | 0 | | | $ | 2,173 | |
| Total | | $ | 2,173 | | | $ | 0 | | | $ | 0 | | | $ | 2,173 | |
|