| **Income Tax (Tables)**                                                                          | 6 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
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| **Income Tax Disclosure [Abstract]**                                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| Summary of differences between income taxes at federal statutory tax rate and effective tax rate | The following table summarizes the major components creating differences between income taxes at the federal statutory and the effective tax rate recorded in the consolidated statements of income for the three and six months ended June 30, 2016 and 2015:Three Months EndedJune 30,Six Months EndedJune 30,  2016201520162015Reconciliation of Federal Statutory to Actual Tax Expense:    Federal statutory income tax at 35%$9,353$9,389$17,496$17,091Tax-exempt interest income(2,104)(1,738)(4,130)(3,167)Basis difference on sale of insurance subsidiary2,252 2,252Stock compensation8101318Earnings on life insurance(453)(223)(970)(485)Tax credits(129)(148)(258)(292)Other41(686)139(727)Actual Tax Expense$6,716$8,856$12,290$14,690Effective Tax Rate25.1%33.0%24.6%30.1% |

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| - References
No definition available.
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| - Definition
Tabular disclosure of the reconciliation using percentage or dollar amounts of the reported amount of income tax expense attributable to continuing operations for the year to the amount of income tax expense that would result from applying domestic federal statutory tax rates to pretax income from continuing operations.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32687-109319
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