Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] |
| | Fair Value Measurements at June 30, 2018 Using | | | | | Quoted Prices in | | | | | | | | | Active Markets | | Significant Other | | Significant | | | | | for Identical | | Observable Inputs | | Unobservable | | | | | Assets (Level 1) | | (Level 2) | | Inputs (Level 3) | | Total | Assets Measured on a Recurring Basis: | | | Available-for-sale debt securities: | | | | | | | | | | | | | | | | | U.S. Treasury and government agencies | | $ | - | | | $ | 57,111 | | | $ | - | | | $ | 57,111 | | Mortgage-backed securities | | | - | | | | 314,431 | | | | - | | | | 314,431 | | State and municipal securities | | | - | | | | 120,531 | | | | - | | | | 120,531 | | Corporate debt | | | - | | | | 84,951 | | | | 6,525 | | | | 91,476 | | Total assets at fair value | | $ | - | | | $ | 577,024 | | | $ | 6,525 | | | $ | 583,549 | |
| | Fair Value Measurements at December 31, 2017 Using | | | | | Quoted Prices in | | | | | | | | | Active Markets | | Significant Other | | Significant | | | | | for Identical | | Observable Inputs | | Unobservable | | | | | Assets (Level 1) | | (Level 2) | | Inputs (Level 3) | | Total | Assets Measured on a Recurring Basis: | | | Available-for-sale debt securities: | | | | | | | | | | | | | | | | | U.S. Treasury and government agencies | | $ | - | | | $ | 55,356 | | | $ | - | | | $ | 55,356 | | Mortgage-backed securities | | | - | | | | 276,498 | | | | - | | | | 276,498 | | State and municipal securities | | | - | | | | 134,849 | | | | - | | | | 134,849 | | Corporate debt | | | - | | | | 64,877 | | | | 6,500 | | | | 71,377 | | Total assets at fair value | | $ | - | | | $ | 531,580 | | | $ | 6,500 | | | $ | 538,080 | |
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Fair Value Measurements, Nonrecurring [Table Text Block] |
| | Fair Value Measurements at June 30, 2018 | | | | | Quoted Prices in Active Markets for Identical Assets (Level 1) | | Significant Other Observable Inputs (Level 2) | | Significant Unobservable Inputs (Level 3) | | Total | Assets Measured on a Nonrecurring Basis: | | | Impaired loans | | $ | - | | | $ | - | | | $ | 32,098 | | | $ | 32,098 | | Other real estate owned and repossessed assets | | | - | | | | - | | | | 5,937 | | | | 5,937 | | Total assets at fair value | | $ | - | | | $ | - | | | $ | 38,035 | | | $ | 38,035 | |
| | Fair Value Measurements at December 31, 2017 | | | | | Quoted Prices in Active Markets for Identical Assets (Level 1) | | Significant Other Observable Inputs (Level 2) | | Significant Unobservable Inputs (Level 3) | | Total | Assets Measured on a Nonrecurring Basis: | | | Impaired loans | | $ | - | | | $ | - | | | $ | 34,901 | | | $ | 34,901 | | Other real estate owned and repossessed assets | | | - | | | | - | | | | 6,701 | | | | 6,701 | | Total assets at fair value | | $ | - | | | $ | - | | | $ | 41,602 | | | $ | 41,602 | |
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Fair Value, by Balance Sheet Grouping [Table Text Block] |
| | June 30, 2018 | | December 31, 2017 | | | Carrying | | | | Carrying | | | | | Amount | | Fair Value | | Amount | | Fair Value | | | (In Thousands) | Financial Assets: | | | | | | | | | | | | | | | | | Level 1 Inputs: | | | | | | | | | | | | | | | | | Cash and due from banks | | $ | 150,086 | | | $ | 150,086 | | | $ | 238,062 | | | $ | 238,062 | | | | | | | | | | | | | | | | | | | Level 2 inputs: | | | | | | | | | | | | | | | | | Available for sale debt securities | | | 577,024 | | | | 577,024 | | | | 531,580 | | | | 531,580 | | Equity securities | | | 993 | | | | 993 | | | | 1,034 | | | | 1,034 | | Federal funds sold | | | 15,585 | | | | 15,585 | | | | 239,524 | | | | 239,524 | | Mortgage loans held for sale | | | 4,605 | | | | 4,605 | | | | 4,459 | | | | 4,459 | | Bank-owned life insurance contracts | | | 129,082 | | | | 129,082 | | | | 127,519 | | | | 127,519 | | | | | | | | | | | | | | | | | | | Level 3 Inputs: | | | | | | | | | | | | | | | | | Available for sale debt securities | | | 6,525 | | | | 6,525 | | | | 6,500 | | | | 6,500 | | Held to maturity debt securities | | | 250 | | | | 250 | | | | 250 | | | | 250 | | Loans, net | | | 6,033,312 | | | | 5,961,354 | | | | 5,756,954 | | | | 5,712,441 | | | | | | | | | | | | | | | | | | | Financial liabilities: | | | | | | | | | | | | | | | | | Level 2 inputs: | | | | | | | | | | | | | | | | | Deposits | | $ | 6,085,682 | | | $ | 6,078,286 | | | $ | 6,091,674 | | | $ | 6,086,085 | | Federal funds purchased | | | 262,659 | | | | 262,659 | | | | 301,797 | | | | 301,797 | | Other borrowings | | | 64,648 | | | | 65,677 | | | | 64,832 | | | | 65,921 | |
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