Segments - Total Assets by Reportable Operating Segment (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
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