Segments - Financial Information of Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	$ 52,611	$ 39,872	$ 96,526	$ 78,537
Interest expense	3,800	3,017	7,456	6,091
NET INTEREST INCOME	48,811	36,855	89,070	72,446
Provision for loan losses	2,059	(1,134)	3,266	(845)
Noninterest income	13,383	11,771	25,467	23,187
Noninterest Expense By Segment	33,634	29,043	65,877	56,821
Depreciation expense	1,299	825	2,329	1,645
Amortization of intangible assets	516	297	864	613
Provision for income taxes	6,498	4,875	11,178	8,646
Net Income	18,188	14,720	31,023	28,753
Operating Segments [Member] | Community Banking [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	52,598	39,845	96,483	78,475
Interest expense	4,056	3,415	7,944	6,897
NET INTEREST INCOME	48,542	36,430	88,539	71,578
Provision for loan losses	2,059	(1,134)	3,266	(845)
Noninterest income	8,869	7,522	16,406	14,375
Noninterest Expense By Segment	29,916	25,092	58,603	49,066
Depreciation expense	1,279	805	2,290	1,607
Amortization of intangible assets	495	274	822	566
Provision for income taxes	6,139	4,637	10,396	8,002
Net Income	17,523	14,278	29,568	27,557
Operating Segments [Member] | Insurance [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	1		1
NET INTEREST INCOME	1		1
Noninterest income	1,328	1,245	2,881	2,766
Noninterest Expense By Segment	1,053	1,044	2,190	2,199
Depreciation expense	14	13	26	25
Amortization of intangible assets	13	13	25	25
Provision for income taxes	88	61	224	181
Net Income	161	114	417	336
Operating Segments [Member] | Wealth Management [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	157	136	298	310
NET INTEREST INCOME	157	136	298	310
Noninterest income	2,917	2,828	5,833	5,764
Noninterest Expense By Segment	2,285	2,442	4,505	4,716
Depreciation expense	6	7	13	13
Amortization of intangible assets	8	10	17	22
Provision for income taxes	271	177	558	463
Net Income	504	328	1,038	860
Eliminations [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	(145)	(109)	(256)	(248)
Interest expense	(256)	(398)	(488)	(806)
NET INTEREST INCOME	111	289	232	558
Noninterest income	269	176	347	282
Noninterest Expense By Segment	$ 380	$ 465	$ 579	$ 840