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Basis of Accounting and Consolidation Basis of Accounting and Consolidation (Acquisitions) (Details) | Nov. 15, 2018 USD ($) $ / shares shares | May 01, 2018 USD ($) $ / shares shares | Mar. 31, 2019 USD ($) $ / shares | Dec. 31, 2018 USD ($) $ / shares
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Agreement And Plan Of Merger [Abstract] |  |  |  |
Common stock, par value (in dollars per share) | $ / shares |  |  | $ 4 | $ 4
Assets | $ |  |  | $ 3,895,619,000 | $ 3,839,734,000
Gross loans | $ |  |  | 2,607,624,000 | 2,658,136,000
Deposits | $ |  |  | $ 3,046,213,000 | $ 2,988,686,000
First BancTrust [Member] |  |  |  |
Agreement And Plan Of Merger [Abstract] |  |  |  |
Percent Of Acquiree Outstanding Stock Being Acquired In Merger |  | 1.00 |  |
Par Value Of Outstanding Stock Being Acquired In Merger | $ / shares |  | $ 0.01 |  |
Right To Receive Value of Cash Option | $ / shares |  | $ 5.00 |  |
Right To Receive Value Of Share Option | shares |  | 0.800 |  |
Shares, Issued | shares |  | 1,643,900 |  |
Shares Issued, Price Per Share | $ / shares |  | $ 37.32 |  |
Aggregate Total Of Cash Paid In Business Combination | $ |  | $ 10,275,000 |  |
SCB Bancorp [Member] |  |  |  |
Agreement And Plan Of Merger [Abstract] |  |  |  |
Percent Of Acquiree Outstanding Stock Being Acquired In Merger | 1.00 |  |  |
Par Value Of Outstanding Stock Being Acquired In Merger | $ / shares | $ 7.50 |  |  |
Right To Receive Value of Cash Option | $ / shares | $ 307.93 |  |  |
Right To Receive Value Of Share Option | shares | 8.0228 |  |  |
Shares, Issued | shares | 1,330,571 |  |  |
Aggregate Total Of Cash Paid In Business Combination | $ | $ 19,046,000 |  |  |
Dividends, Cash | $ | $ 25,000,000 |  |  |

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