Segments - Financial Information of Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	$ 57,808	$ 53,669	$ 168,678	$ 150,195
Interest expense	6,353	4,073	17,877	11,529
NET INTEREST INCOME	51,455	49,596	150,801	138,666
Provision for loan losses	2,516	3,206	12,379	6,473
Noninterest income	13,448	12,481	41,713	37,948
Noninterest expense	32,780	32,138	102,641	98,014
Depreciation expense	1,284	1,211	3,723	3,540
Amortization of intangible assets	375	480	1,243	1,345
Provision for income taxes	7,367	6,407	18,795	17,584
Net Income	20,581	18,635	53,733	49,658
Operating Segments | Community Banking
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	57,804	53,625	168,661	150,108
Interest expense	6,433	4,200	18,085	12,144
NET INTEREST INCOME	51,371	49,425	150,576	137,964
Provision for loan losses	2,516	3,206	12,379	6,473
Noninterest income	9,548	8,651	28,468	25,056
Noninterest expense	28,889	28,941	90,499	87,542
Depreciation expense	1,269	1,192	3,678	3,482
Amortization of intangible assets	359	460	1,189	1,283
Provision for income taxes	7,347	6,139	18,364	16,534
Net Income	20,539	18,138	52,935	47,706
Operating Segments | Insurance
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	1	1	2	2
NET INTEREST INCOME	1	1	2	2
Noninterest income	1,119	1,197	3,836	4,079
Noninterest expense	1,097	1,098	3,455	3,288
Depreciation expense	11	13	33	39
Amortization of intangible assets	12	13	37	38
Provision for income taxes	(1)	26	110	250
Net Income	1	48	203	466
Operating Segments | Wealth Management
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	98	108	343	406
NET INTEREST INCOME	98	108	343	406
Noninterest income	2,563	2,806	7,936	8,639
Noninterest expense	2,591	2,210	7,334	6,716
Depreciation expense	4	6	12	19
Amortization of intangible assets	4	7	17	24
Provision for income taxes	21	242	321	800
Net Income	41	449	595	1,486
Eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	(95)	(65)	(328)	(321)
Interest expense	(80)	(127)	(208)	(615)
NET INTEREST INCOME	(15)	62	(120)	294
Noninterest income	218	(173)	1,473	174
Noninterest expense	$ 203	$ (111)	$ 1,353	$ 468