Segments - Financial Information of Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	$ 40,605	$ 38,581	$ 119,142	$ 114,977
Interest expense	3,076	3,307	9,167	11,438
NET INTEREST INCOME	37,529	35,274	109,975	103,539
Provision for loan losses	1,454	3,419	608	6,749
Noninterest income	11,931	12,542	35,118	40,215
Noninterest expense	27,282	26,729	84,103	84,055
Depreciation expense	898	835	2,543	2,667
Amortization of intangible assets	260	379	873	1,223
Provision (benefit) for income taxes	4,906	4,207	13,552	10,380
Net Income	14,660	12,247	43,414	38,680
Operating Segments [Member] | Community Banking [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	40,581	38,540	119,055	114,733
Interest expense	3,435	3,949	10,332	13,403
NET INTEREST INCOME	37,146	34,591	108,723	101,330
Provision for loan losses	1,454	3,419	608	6,749
Noninterest income	7,742	8,321	22,118	27,144
Noninterest expense	23,691	22,404	72,756	70,293
Depreciation expense	878	816	2,485	2,609
Amortization of intangible assets	238	355	805	1,148
Provision (benefit) for income taxes	4,577	4,027	12,579	10,004
Net Income	14,050	11,891	41,608	37,671
Operating Segments [Member] | Insurance [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	0	0	1	1
Interest expense	0	0	0	0
NET INTEREST INCOME	0	0	1	1
Provision for loan losses	0	0	0	0
Noninterest income	1,496	1,459	4,262	4,406
Noninterest expense	1,127	1,366	3,327	4,002
Depreciation expense	13	12	38	35
Amortization of intangible assets	13	13	38	38
Provision (benefit) for income taxes	120	18	301	56
Net Income	223	50	559	276
Operating Segments [Member] | Wealth Management [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	109	137	419	411
Interest expense	0	0	0	0
NET INTEREST INCOME	109	137	419	411
Provision for loan losses	0	0	0	0
Noninterest income	2,748	2,744	8,511	8,130
Noninterest expense	2,245	2,395	6,961	7,428
Depreciation expense	7	7	20	23
Amortization of intangible assets	9	11	30	37
Provision (benefit) for income taxes	209	162	672	320
Net Income	387	306	1,247	733
Eliminations [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	(85)	(96)	(333)	(168)
Interest expense	(359)	(642)	(1,165)	(1,965)
NET INTEREST INCOME	274	546	832	1,797
Provision for loan losses	0	0	0	0
Noninterest income	(55)	18	227	535
Noninterest expense	219	564	1,059	2,332
Depreciation expense	0	0	0	0
Amortization of intangible assets	0	0	0	0
Provision (benefit) for income taxes	0	0	0	0
Net Income	$ 0	$ 0	$ 0	$ 0