Segments - Financial Information of Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	$ 53,669	$ 40,605	$ 150,195	$ 119,142
Interest expense	4,073	3,076	11,529	9,167
NET INTEREST INCOME	49,596	37,529	138,666	109,975
Provision for loan losses	3,206	1,454	6,473	608
Noninterest income	12,481	11,931	37,948	35,118
Noninterest expense	32,138	27,282	98,014	84,103
Depreciation expense	1,211	898	3,540	2,543
Amortization of intangible assets	480	260	1,345	873
Provision for income taxes	6,407	4,906	17,584	13,552
Net Income	18,635	14,660	49,658	43,414
Operating Segments [Member] | Community Banking [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	53,625	40,581	150,108	119,055
Interest expense	4,200	3,435	12,144	10,332
NET INTEREST INCOME	49,425	37,146	137,964	108,723
Provision for loan losses	3,206	1,454	6,473	608
Noninterest income	8,651	7,742	25,056	22,118
Noninterest expense	28,941	23,691	87,542	72,756
Depreciation expense	1,192	878	3,482	2,485
Amortization of intangible assets	460	238	1,283	805
Provision for income taxes	6,139	4,577	16,534	12,579
Net Income	18,138	14,050	47,706	41,608
Operating Segments [Member] | Insurance [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	1		2	1
NET INTEREST INCOME	1		2	1
Noninterest income	1,197	1,496	4,079	4,262
Noninterest expense	1,098	1,127	3,288	3,327
Depreciation expense	13	13	39	38
Amortization of intangible assets	13	13	38	38
Provision for income taxes	26	120	250	301
Net Income	48	223	466	559
Operating Segments [Member] | Wealth Management [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	108	109	406	419
NET INTEREST INCOME	108	109	406	419
Noninterest income	2,806	2,748	8,639	8,511
Noninterest expense	2,210	2,245	6,716	6,961
Depreciation expense	6	7	19	20
Amortization of intangible assets	7	9	24	30
Provision for income taxes	242	209	800	672
Net Income	449	387	1,486	1,247
Eliminations [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	(65)	(85)	(321)	(333)
Interest expense	(127)	(359)	(615)	(1,165)
NET INTEREST INCOME	62	274	294	832
Noninterest income	(173)	(55)	174	227
Noninterest expense	$ (111)	$ 219	$ 468	$ 1,059