Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] |
| | Fair Value Measurements at September 30, 2017, Using | | | | | 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 Recurring Basis: | | (In Thousands) | Available-for-sale securities: | | | | | | | | | | | | | | | | | U.S. Treasury and government sponsored agencies | | $ | - | | | $ | 56,778 | | | $ | - | | | $ | 56,778 | | Mortgage-backed securities | | | - | | | | 243,743 | | | | - | | | | 243,743 | | State and municipal securities | | | - | | | | 134,804 | | | | - | | | | 134,804 | | Total assets at fair value | | $ | - | | | $ | 435,325 | | | $ | - | | | $ | 435,325 | |
| | Fair Value Measurements at December 31, 2016, Using | | | | | 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 Recurring Basis: | | (In Thousands) | Available-for-sale securities | | | | | | | | | | | | | | | | | U.S. Treasury and government sponsored agencies | | $ | - | | | $ | 46,254 | | | $ | - | | | $ | 46,254 | | Mortgage-backed securities | | | - | | | | 227,190 | | | | - | | | | 227,190 | | State and municipal securities | | | - | | | | 139,930 | | | | - | | | | 139,930 | | Corporate debt | | | - | | | | 9,001 | | | | - | | | | 9,001 | | Total assets at fair value | | $ | - | | | $ | 422,375 | | | $ | - | | | $ | 422,375 | |
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Fair Value Measurements, Nonrecurring [Table Text Block] |
| | Fair Value Measurements at September 30, 2017, Using | | | | | 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: | | (In Thousands) | Impaired loans | | $ | - | | | $ | - | | | $ | 41,114 | | | $ | 41,114 | | Other real estate owned and repossessed assets | | | - | | | | - | | | | 3,888 | | | | 3,888 | | Total assets at fair value | | $ | - | | | $ | - | | | $ | 45,002 | | | $ | 45,002 | |
| | Fair Value Measurements at December 31, 2016, Using | | | | | 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: | | (In Thousands) | Impaired loans | | $ | - | | | $ | - | | | $ | 37,437 | | | $ | 37,437 | | Other real estate owned and repossessed assets | | | - | | | | - | | | | 4,988 | | | | 4,988 | | Total assets at fair value | | $ | - | | | $ | - | | | $ | 42,425 | | | $ | 42,425 | |
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Fair Value, by Balance Sheet Grouping [Table Text Block] |
| | September 30, 2017 | | December 31, 2016 | | | Carrying Amount | | Fair Value | | Carrying Amount
| | Fair Value | | | (In Thousands) | Financial Assets: | | | | | | | | | | | | | | | | | Level 1 inputs: | | | | | | | | | | | | | | | | | Cash and due from banks | | $ | 166,150 | | | $ | 166,150 | | | $ | 623,562 | | | $ | 623,562 | | | | | | | | | | | | | | | | | | | Level 2 inputs: | | | | | | | | | | | | | | | | | Available for sale debt securities | | | 435,325 | | | | 435,325 | | | | 422,375 | | | | 422,375 | | Held to maturity debt securities | | | 36,891 | | | | 37,406 | | | | 25,052 | | | | 25,431 | | Restricted equity securities | | | 1,038 | | | | 1,038 | | | | 1,024 | | | | 1,024 | | Federal funds sold | | | 182,841 | | | | 182,841 | | | | 160,435 | | | | 160,435 | | Mortgage loans held for sale | | | 4,971 | | | | 5,033 | | | | 4,675 | | | | 4,736 | | Bank owned life insurance contracts | | | 126,722 | | | | 126,722 | | | | 114,388 | | | | 114,388 | | | | | | | | | | | | | | | | | | | Level 3 inputs: | | | | | | | | | | | | | | | | | Debt securities held to maturity | | | 50,508 | | | | 51,923 | | | | 37,512 | | | | 37,871 | | Loans, net | | | 5,570,306 | | | | 5,564,250 | | | | 4,859,877 | | | | 4,872,689 | | | | | | | | | | | | | | | | | | | Financial liabilities: | | | | | | | | | | | | | | | | | Level 2 inputs: | | | | | | | | | | | | | | | | | Deposits | | $ | 5,796,901 | | | $ | 5,793,324 | | | $ | 5,420,311 | | | $ | 5,417,320 | | Federal funds purchased | | | 254,880 | | | | 254,880 | | | | 355,944 | | | | 355,944 | | Other borrowings | | | 54,975 | | | | 56,996 | | | | 55,262 | | | | 54,203 | |
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