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Segments - Total Assets by Reportable Operating Segment (Detail) - USD ($) $ in Thousands | Mar. 31, 2016 | Dec. 31, 2015
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Segment Reporting, Asset Reconciling Item [Line Items] |  |
Total Assets | $ 6,479,162 | $ 6,318,354
Operating Segments | Community Banking |  |
Segment Reporting, Asset Reconciling Item [Line Items] |  |
Total Assets | 6,467,331 | 6,305,046
Operating Segments | Insurance |  |
Segment Reporting, Asset Reconciling Item [Line Items] |  |
Total Assets | 7,925 | 9,619
Operating Segments | Wealth Management |  |
Segment Reporting, Asset Reconciling Item [Line Items] |  |
Total Assets | $ 3,906 | $ 3,689

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