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Basis of Accounting and Consolidation Basis of Accounting and Consolidation (Acquisitions) | Sep. 08, 2016 USD ($) $ / shares shares | Sep. 30, 2017 $ / shares | Dec. 31, 2016 $ / shares
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Agreement And Plan Of Merger FCLB [Abstract] |  |  |
Common stock, par value (in dollars per share) | $ / shares |  | $ 4 | $ 4
First Clover Leaf [Member] |  |  |
Branch Purchase and Assumption Agreement ONB [Abstract] |  |  |
Fair value of loans | $ 438,265,000 |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits | $ 536,686,000 |  |
Agreement And Plan Of Merger FCLB [Abstract] |  |  |
Percent Of Acquiree Outstanding Stock Being Acquired In Merger | 1.00 |  |
Percentage of business acquisition consideration paid in cash | 25.00% |  |
Right To Receive Value of Cash Option | $ / shares | $ 12.87 |  |
Aggregate Total Of Cash Paid In Business Combination | $ 22,545,000 |  |
Portion of Business Acquisition Consideration Paid In Common Stock | 75.00% |  |
Right To Receive Value Of Share Option | shares | 0.495 |  |
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares | 2,600,616 |  |

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