Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Financial information for operating segments
Net interest income	$ 33,132	$ 32,911	$ 99,385	$ 96,713
Provision for loan losses	4,625	5,500	14,125	16,350
Noninterest Income	18,014	18,395	50,639	51,770
Noninterest Expense	38,631	36,958	111,962	104,596
Income before income taxes	7,890	8,848	23,937	27,537
Income taxes	853	2,316	4,581	7,695
Net income	7,037	6,532	19,356	19,842
Assets	4,164,606	4,136,474	4,164,606	4,136,474	4,202,008
Goodwill	184,859	184,879	184,859	184,879	184,879
Community Banks [Member]
Financial information for operating segments
Net interest income	33,444	33,172	100,210	97,492
Provision for loan losses	4,659	5,508	14,176	16,388
Noninterest Income	15,387	15,773	42,385	44,948
Noninterest Expense	36,001	34,657	104,403	98,755
Income before income taxes	8,171	8,780	24,016	27,297
Income taxes	1,203	2,345	4,990	7,731
Net income	6,968	6,435	19,026	19,566
Assets	4,105,716	4,081,641	4,105,716	4,081,641
Goodwill	182,076	182,096	182,076	182,096
Insurance [Member]
Financial information for operating segments
Net interest income	23	22	71	84
Provision for loan losses
Noninterest Income	887	871	2,957	2,812
Noninterest Expense	786	754	2,362	2,211
Income before income taxes	124	139	666	685
Income taxes	48	54	258	266
Net income	76	85	408	419
Assets	10,725	9,452	10,725	9,452
Goodwill	2,783	2,783	2,783	2,783
Wealth Management [Member]
Financial information for operating segments
Net interest income	314	326	1,018	962
Provision for loan losses	(34)	(8)	(51)	(38)
Noninterest Income	1,720	1,731	5,234	3,952
Noninterest Expense	1,661	1,447	4,773	3,334
Income before income taxes	407	618	1,530	1,618
Income taxes	51	180	340	487
Net income	356	438	1,190	1,131
Assets	35,172	39,876	35,172	39,876
Goodwill
Other [Member]
Financial information for operating segments
Net interest income	(649)	(609)	(1,914)	(1,825)
Provision for loan losses
Noninterest Income	20	20	63	58
Noninterest Expense	183	100	424	296
Income before income taxes	(812)	(689)	(2,275)	(2,063)
Income taxes	(449)	(263)	(1,007)	(789)
Net income	(363)	(426)	(1,268)	(1,274)
Assets	12,993	5,505	12,993	5,505
Goodwill