| **Business Combinations (Tables)**                                                              | 3 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
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| **Business Acquisition [Line Items]**                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
| Schedule of pro forma information from acquisition                                              | The following schedule includes pro forma results for the periods ended December 31, 2014 and 2013 as if the CFS and Community acquisitions had occurred as of the beginning of the comparable prior annual reporting period.  2014 2013Total revenue (net interest income plus other income)$263,070 $253,668Net income$61,572 $39,979Net income available to common shareholders$61,572 $37,599Earnings per share:   Basic$1.63 $0.98Diluted$1.61 $0.97                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| Merger with Community Bancshares, Inc.                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
| **Business Acquisition [Line Items]**                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
| Schedule of preliminary valuations of the fair value of assets acquired and liabilities assumed | Based on preliminary valuations of the fair value of tangible and intangible assets acquired and liabilities assumed, which are based on assumptions that are subject to change, the purchase price for the Community acquisition is detailed in the following table.  Prior to the end of the one year measurement period for finalizing the purchase price allocation, if information becomes available which would indicate adjustments are required to the purchase price allocation, such adjustments will be included in the purchase price allocation retrospectively.  Fair ValueCash and cash equivalents $4,124Interest -bearing time deposits 16,526Investment Securities, available for sale 76,807Loans 145,064Premises and equipment 3,610Federal Home Loan Bank stock 1,950Interest receivable 767Cash surrender value of life insurance 3,266Other real estate owned 6,662Taxes, deferred and receivable 3,348Other assets 167Deposits (228,424)Interest payable (98)Other liabilities (3,014)Net tangible assets acquired 30,755Core deposit intangible 4,658Goodwill 13,776Purchase price $49,189 |

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| - Definition
Tabular disclosure of pro forma results of operations for a material business acquisition or series of individually immaterial business acquisitions that are material in the aggregate.
+ References
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| - Definition
Tabular disclosure of the amounts recognized as of the acquisition date for each major class of assets acquired and liabilities assumed. May include but not limited to the following: (a) acquired receivables; (b) contingencies recognized at the acquisition date; and (c) the fair value of noncontrolling interests in the acquiree.
+ References
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