Segments - Financial Information of Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	$ 39,872	$ 38,553	$ 78,537	$ 76,396
Interest expense	3,017	3,957	6,091	8,131
NET INTEREST INCOME	36,855	34,596	72,446	68,265
Provision for loan losses	(1,134)	1,023	(845)	3,330
Noninterest income	11,771	12,867	23,187	27,673
Noninterest expense	29,043	27,077	56,821	57,325
Depreciation expense	825	896	1,645	1,833
Amortization of intangible assets	297	413	613	844
Provision (benefit) for income taxes	4,875	3,951	8,646	6,173
Net Income	14,720	14,103	28,753	26,433
Operating Segments [Member] | Community Banking [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	39,845	38,505	78,475	76,194
Interest expense	3,415	4,663	6,897	9,454
NET INTEREST INCOME	36,430	33,842	71,578	66,740
Provision for loan losses	(1,134)	1,023	(845)	3,330
Noninterest income	7,522	8,467	14,375	18,823
Noninterest expense	25,092	21,786	49,066	46,427
Depreciation expense	805	876	1,607	1,795
Amortization of intangible assets	274	387	566	792
Provision (benefit) for income taxes	4,637	4,592	8,002	7,438
Net Income	14,278	13,645	27,557	25,781
Operating Segments [Member] | Insurance [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	0	0	0	1
Interest expense	0	0	0	0
NET INTEREST INCOME	0	0	0	1
Provision for loan losses	0	0	0	0
Noninterest income	1,245	1,349	2,766	2,947
Noninterest expense	1,044	1,105	2,199	2,552
Depreciation expense	13	12	25	22
Amortization of intangible assets	13	13	25	26
Provision (benefit) for income taxes	61	77	181	122
Net Income	114	142	336	226
Operating Segments [Member] | Wealth Management [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	136	135	310	273
Interest expense	0	0	0	0
NET INTEREST INCOME	136	135	310	273
Provision for loan losses	0	0	0	0
Noninterest income	2,828	2,812	5,764	5,386
Noninterest expense	2,442	2,389	4,716	4,878
Depreciation expense	7	8	13	16
Amortization of intangible assets	10	13	22	26
Provision (benefit) for income taxes	177	221	463	313
Net Income	328	316	860	426
Eliminations [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Interest income	(109)	(87)	(248)	(72)
Interest expense	(398)	(706)	(806)	(1,323)
NET INTEREST INCOME	289	619	558	1,251
Provision for loan losses	0	0	0	0
Noninterest income	176	239	282	517
Noninterest expense	465	1,797	840	3,468
Depreciation expense	0	0	0	0
Amortization of intangible assets	0	0	0	0
Provision (benefit) for income taxes	0	(939)	0	(1,700)
Net Income	$ 0	$ 0	$ 0	$ 0